Everything Mirage said is quite applicable, especially the part about what you consider handle it well to be.

I'm not sure you're going to find what you're looking for right now though. Most PC games end up being console ports that don't really push the PC hardware at all, or worse, push it because they're so poorly optimized for PC. If you're looking for a game that will bring a PC to it's knees like Doom 3 or Crysis on max settings would when they were released, Metro 2033 is about all there is now.

Maybe Battlefield 3 would do it on max settings, but I'm not too sure. I haven't seen any benchmarks for it, but Dice said if you could run Bad Company 2 you could run Battlefield 3, and I'd say Metro is definitely more taxing on my system than Bad Company 2 was. The Battlefield series also tends to be pretty optimized for multiple cores now, so I'd imagine that if you don't have a quad core processor you'll probably find yourself limited more by your CPU on max settings than the GPU.