Build a desktop.
I know it sounds crazy. I know it does. 6 months ago, I'd have said the same thing. But I asked a buddy of mine who's done it before if he thought it was a good idea for me. He said to go for it. One of my specific goals was to build something that I could expect to run Skyrim near maximum settings. I have a quad-core 3.4 ghz cpu and an ATI Radeon 5770 gpu, which basically means my computer is a freaking thug. I may be buying a second Radeon 5770 and taking advantage of its crossfire support. If I do this, I am ABSOLUTELY sure my computer will be able to run Skyrim at maximum settings. Seriously, my comp eats Crysis, Dead Space 2, Bulletstorm, Starcraft 2, and Deus Ex: Human Revolution for breakfast. I play all these games at maximum settings without seeing so much as a hiccup. (I'm having trouble with RAGE, but that's because it needs some serious patching, not because of my rig). This beast cost me less than $800 (Not including the mouse, keyboard, etc.)
I know that might sound like a bit much, but think about how much more useful a pc is than an Xbox.
If you need help building it, check out Reddit.com/r/buildapc and read the BaPC Beginner's Guide.
After that, read this: http://www.tomshardware.com/reviews/build-your-own-pc,2601.html
Then get on Newegg and get started. But be sure to get in touch with somebody who really does this stuff. They'll be able to think of stuff you wouldn't, and help you avoid a lot of headaches. If you don't know anyone personally, the guys on reddit.com/r/buildapc are good people; they'll help you out. But I'm telling you, the computer I'm using to type this is one of the best investments I've ever made.
Good luck, bro.