Should I Buy an XBOX now?

The XBOX is so cheap now. You can pretty much get it for $100 after rebates and promotions, but it's also such an old console. Yes there are new things like the kinect for it.

If I were to get a new system for gaming, should I:

a) get an XBOX

b) get a PS3

c) get a PC and game on that

d) other options?