For Crysis, Nvidia is the way to go for the moment (you stated you wanted to run this) as the drivers have been worked with while making the game to make sure they push the game a long as well as possible, though ATI won't be far behind, so it won't matter really.
Its weird how developers shine towards one kind of graphics vendor to work with.
For instance Valve prefers working with ATI.
Is it just because they get paid to sponser?