No, I don't consider this the same as my anime post. Yes, it's long and full of personal opinions and such and in fact mostly borrowed from a post I made elsewhere. I'm a big FF person, I'm posting it here anyway ;3
Many -- if not most -- FF fans are aware of the influence Dungeons and Dragons had on the franchise, especially the first Final Fantasy. What may not be as clear is the sheer amount of that influence. In actuality, Final Fantasy feels and plays like a virtual replica of a hybrid between 1e and BEMCI. Most elements are shared between the two versions of the tabletop rpg; the classes borrow from the D&D boxed sets, the monsters from AD&D.
While some of similarities are painfully self-evident (level-based advancement, dungeon crawling, collecting XP, treasure and sometimes magic items from defeated monsters, and the multiple-character party), these are also fairly generic points. Here I plan to detail the more nuts-and-bolts parallels.
There may be a few things I'll miss, as I'm working mostly from memory
These are virtually self-explanatory, being as the classes available in the game are virtually identical to those in the Mentzer boxed sets (Cleric, Fighter, Magic-User, Thief, and -- introduced in later boxes -- the oddly-named Mystic) with a single exception, detailed below. The breakdown of classes is:
Fighter: Swings the big weapons, wears the beast armour, uses the best magical swords and stomps on your face. Essentially the D&D Fighter.
Thief: The sad thing is, until you hit the higher levels the D&D Thief is about as useful as tits on a mule. This sorry state of affairs is mirrored well in the FF Thief, which is little more than a weak Fighter until you receive the class upgrades from Bahamut. (more on class upgrades, and Bahamut, later.)
Monk (or Black Belt, if you like): The D&D Mystic, with the emphasis on no armour and dishing out damage with one's fists.
White Mage: Here we find the D&D Cleric. While one notable difference has been made -- the lack of armour, possibly to distinguish the White Mage from the Red Mage -- the White Mage otherwise mirrors the Cleric to an amazing degree. Like Clerics, White Mages focus on support magics, can use bludgeoning weapons (I miss White Mages having the ability to swing warhammers in later games, let me tell you!) -- and the apparently hideously-overspecialized Dia series of anti-undead spells in fact serve to emulate the Cleric's ability to "turn" and destroy undead creatures.
Black Mage: The Magic-User class, purveyor of increasing attack attributes and dishing out healthy heaping doses of magic-induced pain. Getting Fira is like reaching a high enough level to cast Fireball for the first time, I swear ~
Red Mage ...?: At first blush, it would appear that the hybrid Red Mage is unique to FF. Alas, this is not the case. D&D also contained three demihuman classes, Dwarf, Elf and Halfling (why yes, early D&D used demihuman species as their class) -- and with it's use of light armour, most weaponry, a decent attack stat and the ability to cast limited magic, the Red Magic beautifully emulates the Elf class, favoured class of those wanting to stab and cast magic even if you don't really like elves, level cap and XP penalty be damned. (I personally got around the elf question by backwards-engineering a human class. I really don't like elves ;3)
VANCIAN MAGIC!!: Aah, that wonderful need to carefully harbour your spell slots per spell level you can cast, lest you run out. Though the D&D "fire-and-forget" system of Vancian magic has been modified to a number of free slots per "day" (for lack of a better word) rather than the spellcasting characters selecting and memorizing/praying for a specific slate of spells per day for the sake of smooth videogaming, it's still a Vancian system. (At that, the FF method was borrowed back for the 3e D&D Sorcerer class.) It's not surprising that eventually Vancian magic was phased out in favour of a point-based system.
Churchly Resurrection: This one was also abolished within a few games as the FF franchise trundled on, in favour of the now-iconic Phoenix Tail/Down. But the need to bring your deceased party members back to a friendly church with powerful clerics to resurrect them -- until you've become powerful enough to cast the magic yourself -- is not only a D&D trope, it's a trope for a reason. PCs die all the damn time in D&D also. At least FF doesn't make you pay through the nose with treasure or a geased quest in return for the privilege ;3
Class Upgrades and Titles: In FF, party members gain a shiny class upgrade and new class title from Bahamut; they're real heroes now, with more oomph at their disposal. This is a well-turned emulation of the D&D "Name Level" -- usually around level 9, sometimes a few later -- wherein the PC gains a new and special title (Fighter -> Knight, Paladin or Avenger, Mystic -> Master, Magic-User -> Wizard, etc. etc.) and new privileges, usually based around owning territory and / or gaining followers. FF, not being a sim game, goes the power route; but the net intent and effect is the same.
Bahamut: Speaking of His Scaliness, Bahamut -- traditionally and originally a giant fish -- as an honourable and good king of well-intentioned wyrms is lifted straight from AD&D, where Bahamut is of course the Platinum Dragon and King of the Metallic (= Good) Dragons. (later games emulate this even further with his greyish colouration and in one case his human guise.) As Bahamut is a creature it is not surprising he was drawn from AD&D rather than D&D; see below.
FF uses a number of generic spells. It also uses a number of spells, names and all, that are pretty much D&D staples (haste; don't leave home without it). Some have been shuffled from clerical (white) to magic-user (black) types for the sake of class balance -- FF doesn't use non-combat spells, after all, so holes in spell lists need to be plugged -- but the spell itself remains.
I'm not going to enumerate every single FF spell and magical item, with commentary; I don't have that kind of patience, to be honest ;3 However, the following lists the FF spells which are iconic D&D spells, ignoring the generic elemental spells because pffft:
Sleep -- just as godly at low levels as the D&D version.
Hold -- hold person and the like
Cloud (called Poison, Scourge, BANE etc in NA editions) -- cloudkill.
Confuse -- confusion. hate this spell, hate it -_-
Death -- could be many things but always seemed to be finger of death to me.
Saber -- Mordenkainen's sword.
Stop -- time stop.
Kill (Doom) -- power word, kill.
Flare -- hello meteor swarm. which is funny, as in later games Flare and Meteor get split up.
(the Dia spells are addressed in the Classes section)
Silence -- love silence when fighting magic-users, yee~ees ~
BaThunder (NulBolt, etc.) -- protection from electricity; similar spells follow pattern.
Invisi -- invisibility.
Dispel -- dispel magic.
... Oh who am I kidding. The spells pretty much map, especially the White Magic as it's so repetitive.
Ditto here; you can basically say "yup, same ideas" with a few exceptions; (A)D&D uses generic names for a lot of this to begin with so there's not a lot of point rambling on about them like an idiot. A few magic items, especially swords, deserve calling out as having names identical to specific named types of magical blades in AD&D, and there a few other iconics hidden in there:
Ice Brand -- Frost Brand
Staff of Power
Wizard's Staff (Spellbinder in DoS) -- probably Staff of the Magi, legendary along with the Staff of Power.
Fun times! For this I'll be using the original FFJ names and cross-referencing more familiar ones where necessary to clarify.
The monsters in FF crib straight from the D&D monster lists and AD&D Monster Manuals in a big way, to the point of many monster names (Beholder, Marilith ...) needing to be changed in the NA editions to avoid lawsuits from TSR. Even once WotC acquired the D&D license and the System Reference Document allowed the use of some creature names, use of the SRD would have required a licensing agreement that Squenix -- rightfully -- would not have so much as looked at. Some were wiggled through in later re-releases, probably due to being made up of generic words (Mind Flayer, Black Pudding, etc.) and re-used by so many games at that point.
That said, here are the special AD&D monsters. It's also worth noting that the undead ability to paralyze, so popular in FF, is lifted from the ghoul/ghast/etc series in (A)D&D. In fact FF takes pretty much all the (A)D&D undead monsters, many of which bear no resemblance to the mythological creatures or words they were based on (lich and wight, for example).
CHAOS. Not as a specific monster, but! The entire gist of D&D could be boiled down to fighting off the encroachment of Chaos and the monsters, warping and corruption that goes with it. Most PCs are Lawful or Neutral and most monsters are Chaotic. The Good/Evil axis of alignment doesn't even get introduced until the AD&D ruleset. So, having the ultimate Big Bad be Chaos is definitely fitting for a D&D-flavoured game.
Lich -- the iconic Terrifying High-Level Undead Horror of AD&D. Just saying. ;3
Marilith -- called "Kary" in original NA FF, no doubt to avoid a lawsuit (or through the fear of one).
Kraken -- generic, yes, but krakens in (A)D&D are intelligent and controlling high-level monsters so I'm including him here.
Tiamat -- much like Bahamut, appears here as a multiheaded dragon instead of her original version. She's blue in FF instead of multicoloured, however, something FF either cared not to emulate, chose not to, or did not wish to risk the wrath of TSR (especially as Tiamat was a major antagonist in the D&D cartoon). I've also heard it said that it was a simple palette limitation.
Warg (Worg) Wolf
Sahuagin (and variations)
Crawler -- sprite is clearly a version of the carrion crawler.
Hill Gigas -- = Hill Giant, of the Hill/Fire/Ice D&D trifecta.
Ankheg (PEDE, Centipede) -- though the sprite is more generic-looking than the D&D monster named ankheg.
Horned Devil (R. GOYLE) -- likely the reddish Horned Devil, later Cornugon.
Pyrolisk -- PERILISK of NES FF likely a lawsuit dodge.
Fire Gigas -- = Fire Giant, of the Hill/Fire/Ice D&D trifecta.
Winter Wolf (FrWOLF)
Mind Flayer (SORCERER, Mindflayer) -- they even look just like them ...
Ice Gigas -- = Ice Giant, of the Hill/Fire/Ice D&D trifecta.
Remorhaz (GrPEDE, Remora, etc)
Beholder (EYE, Evil Eye) -- oh, this one is/was a lawsuit just begging to happen ...
Desert Bulette (ANKLYO, Desert Baretta)
Bulette (R. ANKLYO, Baretta)
Water Naga -- of the Guardian/Spirit/Water AD&D naga trifecta.
Spirit Naga -- of the Guardian/Spirit/Water AD&D naga trifecta.
Death Knight (EVILMAN, Doom Knight) -- ahahahahhaa treading on the iconic Lord Soth from Dragonlance ~
Gorgimera (JIMERA, Rhyos)
This list of course omits generic animals and monsters (wolf, goblin, ghost, orge etc) shared between both games.
In some cases only the name was swiped and applied to a more generic-looking creature of the right type (chimera/gorgimera, for example; the AD&D gorgimera is a hybrid of a chimera and a gorgon, an iron-scaled poison-breathing ox).
Additionally, many of the dragons -- and certainly the identifications by colour -- are lifted straight from (A)D&D.
So, there you have it. I may have missed a few things, but these are in my opinion the Big Ones. If there is any element in Final Fantasy -- an item, an event, a class, a monster -- you would like to ask about, feel free! I'll see what I can find :3