For me the best currently are Bioshock 1 and 2, and Dear Esther. This work almost as good as any native VR app in terms of pressence. I’ve had some success with others like Metro 2033, System Shock 2, Stanley Parable, Aliens Colonial Marines, but they cannot beat those mentioned.
The only thing with Bioshock: you have to be sure it’s set to 1080p and reset any settings I did in Nvidia-Controllpanel. (to force AA, for example). In the first case the game won’t start and in the second, the game can freeze in g3d-mode. (at least in BS 1)
Also Skyrim and Oblivion are really enjoyable in vr, especially when you have a powerfull card which delivers smooth framerates. Fallout 3 too, but unfortunately this game crashes after a few minutes. I hope this is a bug which can be solved easily by Ralf. I can’t wait to play Fallout longer than 3 to 10 minutes. ;-)
Skyrim is great imo. I don’t seem to be as bothered by low fps as some prople, and I don’t think I’ve seen anything that could comepare to a modded skyrim. Just walking around in the cities with the amazing mountain backdrops looking at the npcs close, is worth the time setting up the game.