I really liked the OG XB 'AA' library. Best of all Xbox gens for me. At the same time I thought Halo was an overrated shallow sort of ugly game, but that was mainly because I was already way into PC FPS, and seeing a low-resolution 30fps console FPS was incredibly underwhelming coming from game series like Unreal Tournament, Half Life, Tribes, etc.
So I was kind of disgusted at how MS basically left PC gaming for dead for at least a solid decade other than token/insulting half baked crap, and actively undermining it with the very act of buying Bungie and cancelling the Mac version of the game, scaling it back for consoles, only releasing PC ports much later with pretty horrible port quality, etc. By the time the 360 came out, I was pretty much done with consoles anyway. It wasn't until PS4 that I decided to grab another console to play some console exclusives I'd missed out on, TLOU, God of War 3 RM, UC 1-4, HZD, etc. Still prefer vastly to play on PC, but don't mind at all playing some greats on PS. Don't think I'll ever buy another XB console, but have to say I am impressed with how they've turned a corner in terms of not crapping on their PC marketplace, and offering cool stuff for their owners like OG/360 BC. Bravo.