Well I'm no programmer, but as I understand it 32 and 64 bit programs are quite different from each other requiring substantially different coding. For one thing they have entirely different ways of addressing memory, hence the ability of using more RAM with 64 bit. While you can run a 32 bit program in a 64 bit OS, through emulation, it doesn't work the other way around.
There's already a 4 gb's patch that ups 32-bit apps allocation size from 2 to 4 gb's. I'm no programmer either, but it shouldn't be THAT difficult.
I've certainly not heard of any. And the fact that they would have separate exe's means that they are essentially two different games.
http://www.giantbomb.com/profile/buckybit/list-of-native-64-bit-pc-games/46-57269/. Crysis/Crysis Warhead, Bioshock 2, S.T.A.L.K.E.R, amongst others. And it's obvious you don't have the slightest idea of how game engines work if you think that changing the executable means creating a new game. Games are far more than their executables (meshes, textures, shaders, sounds, music...), do you REALLY think that all of that must be ported, too?
It won't do you any good if you're still only using a 32 bit program.
I haven't given up hope yet. Plus, gaming is not the only reason I get them.