I don't recommend the 360. Most shooters on this system are dumb'd down for the console, and most, if not all, are out for the PC. The PC has more power, and can do many things the 360 can't.
Get a Wii if you like classics (you can buy most of them for around 10 dollars, based on how popular it is.
Overall decision: UPGRADE YOUR PC, DAMNIT!