Is it worth getting an xbox 360 for console exclusives? Also another question?

I'm a huge Halo fan, although I sold my 360 long ago (I haven't played a Halo game since Halo 3).

I'm a PC gamer now, I have a high end gaming PC so I really have no need for a console unless it's an exclusive. I'm kind of torn over this. In your opinion is an xbox 360 worth getting for Halo 4 and future console exclusives? I heard that Halo 5 will be running on Microsoft's next gen console, so that sucks that I may have to buy another system.. but this console might not be coming out for years right?

Without a doubt if I got a 360 I would buy a used one on Craigslist or wait for a Black Friday/Cyber Monday deal. What is the reasonable price for the slim versions nowadays? Is 4gb enough for my needs? It may seem like it at first, but I don't know if I'll be downloading console exclusive demo's or dlc.

Jeez, and there's also the matter of getting a PS3 over a 360, since they have a lot more console exclusives I want to try (Killzone, Uncharted, Nier, MGS, ect) but I hear the PS3 runs on lesser hardware and doesn't have a very good online, and there's also the matter of security. What do you guys think about this too? I think despite this I would still get a 360, since I have never owned a PS3 and Halo 4 means a lot to me.

Sorry for asking so many questions but hopefully you guys can help. Thank you!

Edit: I made a huge misunderstanding. When I said console exclusives I didn't just mean only on xbox, I meant only on consoles (therefore I can't get it on pc) I'm fine with cross platform games, hope that widens my search.
Edited by apav - 11/3/12 at 7:11am

Well I feel kind of discouraged for just getting it for Halo 4 right now. But I also may pick up Gears 3, and do you guys know if any other popular console exclusives that are coming out soon?

Just basically want to get more out of my 360 than Halo 4. Because I'm sure after I beat the campaign and go on to multiplayer, I'll be playing it casually on and off.

I do want to play Halo 4, but I'm afraid after I beat the campaign and playing on and off multiplayer I won't get my money's worth. That's why I'm looking for other console exclusives to justify my purchase! I'm torn because I want to play Halo 4, but I don't want to buy a 360 (even used are like $150 right?) for just one game.