So if you want a more dramatically enhanced version of the campaigns/co-op: You have the MCC, which can be bought for close to nothing digitally at this point. Those campaigns have been fairly solid since launch, and are it totally fine shape now. 60 fps and the Halo 2 Anniversary improvements are a difference worth it for many.
If you want multiplayer in its original format for the 360 games, you now have access to it on XB1 with all add-ons made free. You can use your original discs.
They done good, all things considered.