based on budget and favorite genre's I'd say a X360. You got Halo, CoD and plenty of other shooters. Forza, Burnout and plenty of other racers.
You also can buy the arcade (or whatever it is called) for $200.
EDIT: after more thought, my second choice for you would be Wii, but that is only because of the cost of Live. I don't suggest the PS3 because of your $300 budget, but if you can find a used one that would be good too. I know my post has been useless.








