Well, yes, there is that option, too. But still, quite a broad range on both 360 and 720. Keep in mind that there are some Xbox and PS3 exclusive games; such as Halo for the 360. Spino showed a bunch of games you can buy if you were to get the PS3, however would cost plenty to buy the lot xD.
Yeah, PC has a lot of exclusive games which I would look into. There is Metro 2033, with Metro: Last Light set for release in March. Minecraft (which you must have heard of) and Terraria which is similar. You have games such as The Binding of Isaac, Awesomenauts, Chivalry and the list goes on and on. What's so wonderful is that Steam has so many PC exclusive games and they're not games which cost a fortune. In fact, most of the games on Steam cost less than £20. Steam also have many sales and deals; Hitman Absolution was 66% off, Sleeping Dogs was 75% off etc. you get the jist. The PC itself may cost a lot, but the games are at a very nice value and Steam has a huge audience, so never expect to be lonely in a multiplayer game.
Just think about it, but don't jump to a conclusion too quick or you will regret it.