Some of those games we know nothing about, so no one can say if your ok. You have an i7 920, with 6GBs of ram, and the GTS460. You should be good. The only possible problem you might have is maxing EVERYTHING out in some of those games at 1080. You should be able to run all of them however.
Diablo 3 you should be ok if the engine is anything like Starcraft 2.
For Portal 2, Half-Life Ep. 3 and Crysis 2, I haven't seen any benchmarks or comments to comment.
MS Flight, if anything like the previous Flight Simulator, could be a resource sink, but I can't remember if it was more taxing on CPU or GPU.