Computer won't run certain games very quickly?

I just finished building a computer, and decided to test it out. I noticed that games like Call of Duty: MW2 and Minecraft run optimally, but games like Sonic Adventure DX and Call of Duty: BO run not so well. It doesn't make sense to me that a late generation Xbox 360 game runs smoother than a Game cube release title. Any help?

Might be the games or might be your pc. Mw2 and Minecraft I can run well on a toaster but BO might need more from the computer. This is usually where your cpu and gfx card come into play. If those are not that great that's probably your problem.