Myst.
They have a new one.
Relatively new.
It's as buggy as shit. Really buggy.
And I love the hell out of it.
It's not small, not really anyways, but it still has that loving familiarity to it. Like the last ones, the game was created with a very acute attention to detail, and the feeling you get when you read, on your own will, a 30+ page journal, and start to understand it and see it come together... it's exhilarating.
It's Myst Online Uru-Live.
The best part is that it has Open Source elements to it. Sure, that opens the doors for wierd and undesirable shiiiiieeeeeeieieieieit, but there's probably a couple good developers out there who keep in the Myst spirit.
Hell, I'd go as far to say that every aspiring developer should play this game. It won't teach you how to properly use a shader engine, or why you should just use Frostbyte for everything, it won't teach you alot of things, but at least it'll teach you how to make a game. It'll teach you how to create a world.
Then you can take that knowledge, and create your world in the Frostbyte 2 engine with top quality shaders and explosion physics and all that jazz, and make something nobody can afford not to play. Yes, I could really go for a game with the same attention to detail Myst has always had, but made with more efficient tools right now.