Another tough call. I currently play games on a PSP, PS2, Xbox, and the computer. I wouldn't give any one of 'em up either.
I love my PSP...great graphics, portable, great when someone's watchin' the t.v. and I want to play a game that's not on the computer.
I have always been a Sony-person, so I love my PS2 and the majority of my games are PS2s.