Is it worth re-buying a 360 for ?
No, not if you're paying $250 + $60. No game is worth $310. Not even Halo 4. If you could borrow a 360 or rent one then rent the game from somewhere for a day or two (single player is only about 6 hours), then it might be worth it if you're a die hard Halo fan.
why do you say it looks amazing? Looks (graphics) just like any good game that has come out in the last year or two.
Not really.
I'm a huge proponent of custom game engines, because it shows that the company who made the game cared enough about the end user experience that they went out of their way to actually write a functional engine and build their game around that. When you write your own engine, you can do exactly what you want. You're only limited by the talent of your programmers, and nothing else.
Case in point, a lot of triple-A hackjobs out there today are built around UDK or idTech. And it shows. Neither UDK nor idTech *really* run well on the 360. They run, acceptably, but it isn't stellar. Textures need to be down sampled because of limited VRAM, shaders need to be reduced in quality because of the limited GPU capabilities. Forget about AA or any of that stuff- you've already maxed the console by the time you have your game running and semi-playable.
ME3 and Borderlands 2 run on the 360, but the quality is inferior to that on the PC. ME3 in particular had some serious issues with texturing (stuff I'm surprised they shipped with)- but that's what you get when your game engine is so brutally unoptimized that you have to down sample textures from 2048x2048 to 256x256 to make it run smoothly.
Halo 4 is borderline PC quality. From a 2006 console. That's one hell of an achievement, if you ask me- pulling that sort of thing off with UDK or idTech would be impossible. I'm not saying that there haven't been "good games" out in the last year, because there's been plenty- but let me put it this way- I've bought more then one title recently where the quality of the graphics has painfully reminded me how old my aging console is. With Halo 4, it made me feel like I'd just bought a new console again. The graphics are that stellar.
-SC