Strictly in terms of gameplay mechanics. Nothing else. Just the basic gameplay structure. By basic gameplay structure I mean Morrowind and Skyrim have the same basic gameplay. Just like Dragon Quest VIII and Lost Odyssey have similar gameplay.

Thoughts?

Speaking in terms of strictly gameplay, I'm going to say Final Fantasy 10.

Dark Souls

I'll say http://www.bay12games.com/dwarves/. The graphics are extremely simple, but the scope of the game is insanely huge, anything can happen.

That's an interesting question. Most of an RPG's mechanics borrow at least a few concepts from others. In my experience whenever they try to stray too far from the beaten path you end up with some metaphysical weirdness that isn't any fun. I'd say the Megaman Battlenetwork games had pretty unique combat, at least for their time. The battles were sort of an actiony collectible card game.

I can't really think of one.
The RPG is a wide genre. But even across a spectrum, it is made to fit into a set of gameplay criteria. The genre can also be split into sub-genres, and some games are more original than others, but they all tend to fit into the RPG genre.... That's why they are RPGs.
The standards being, for example...
Japanese: FF series
Western: TES games
Strategy: Shining Force
Action: Dark Souls, Zelda
And there's also the sub-genres like, MMO and Dungeon Crawlers.

Earthbound uses the same combat ideas as Shadowrun (dice roll)... despite having different combat gameplay.
Dark Souls plays like Twilight Princess the same way. (block, counter)

RPGs that are regarded as unique are usually because of the storyline, setting, or some sort of weird characteristic that adds other non-RPG elements into the game..... But they usually always have one of the standard RPG gameplay types.



So, strictly thinking about gameplay, not a single game stands out. They all borrow and evolve from each other, and borrow from other genres differently.

Huh?
FFX has identical gameplay with many other RPGs.

I'm going to go with Dungeons and Dragons.

Pluto nailed it. At least partially. I can't really think of one either. Shenmue is one my roommate named kind if tentatively, and yet I have not played it so I cannot really say one way or another.

As far as Zelda and the Souls series? I wouldn't say they have similar gameplay. Even in a basic sense. You do not traverse a Souls game with puzzle solving in the Zelda style. Too much is different in there, from item usage and function to the fundamentals of swordplay and stamina management. Care to explain that one briefly Pluto?

Honestly if I had to name a unique RPG type it would likely be the Souls Series, mostly because of the multiplayer component. Yet, it DOES have similarities to a lot of other games and I can't say that component can or cannot differentiate it enough to stand out. Admittedly Zelda does have a few similarities as well.

Possibly the Heroes of Might and Magic series, although it barely qualifies as an RPG. It also is basically a turn based strategy RPG.

Would Vampire the Masquerade qualify at all? My roommate feels it was quite unique as well, but again idk.

Seems like there is a very predefined range of gameplay types for RPGs.