Check out the games. The one that has the games you like best is the best console for you. For me it would be PS2 (GTA3 and GT3) but that upcoming mech game for Xbox looks pretty sweet too. Just don't buy Blood Wake if you get the Xbox, yuck!
We just had two threads go by that debated consoles pretty well. Try searching for PS2/Xbox/Gamecube on the General Forum. But in short it's basically just look at the games, and forget about the hardware. Get the console that contains the games you want. Each console does cater towards a specific genre of games. I'd try not to let price be too influential of a factor either. An extra $50 here or there is nothing considering how much time you'll probably end up logging on the console.