The word game is list at m-w.com as a activity that is a diversion. Video game's definition over there is a little out dated, but niether mentions fun.
Akuma's list is great for some games as art. It's funny that you didn't mention FFVIII, it's nowhere near my favorite in the series but it tried to do something that no other FF game has (that I can think of). Levels are mostly irrelevant in FFVIII, while this kills the fun of going back and slaughtering earlier opponents, it takes the grind out of role playing and can make the game more immersive if you ignore stats and stuff like that. Oblivion does this too.
Metal Gear Solid 1 to me is one of the most immersive and dramatic games that Akuma mentions, the story is there but the real experience is the gameplay. The sequels got more and more melodramatic, but the first one is a good example of gameplay affecting the players emotions more than the story, with out relying completely on killing-shoot-em-up action.
Like I said earlier, SMB is like a piece of art from a master of gameplay and surrealism. God I am such a Shiggy groupie, but you know what he deserves it. SMB1&3 and SM64 all fall into this, galaxy is coming along nicely.
Elebits would have been perfect with out the cutscenes. If they had only done the narrative a little differently I think that game would have been recieved and reviewed much better than it was. The gameplay is like what you would expect a family movie should play out like. Twisting, turning, lifting, searching. If you could get over the flaw of the bad narrative, this game would have you making faces that you hadn't made playing a new video game in a long time.
Mature isn't really the right word, because it is used too many different ways when relating to games. Let me use it in a sentence a little differently, maybe that will make my purpose a little more clear:
Gaming as an artform is maturing very slowly. This maturity is key for a mainstream audience to become part of deeper gameplay experiences. Maybe Nintendo's casual friendly approach will help it, maybe it will be MS's media-center features and rich online experience, maybe it will be Sony's larger format and social network (Home), or maybe it will still progress slowly. I think in the next couple years we will begin to start seeing the true next level of the artform.
I would cite regulation, but I know you will simply ignore it.
