It's two remakes, the one that is built like an oil rig or something is a remake of one in Halo 2. I liked all the new maps, but Avalanche (Sidewinder) is veeery boring if you're just you against four guys in team duel if the other members of your team quit since they couldn't handle the pressure...
What I'd like to see a remake of though is Death Island that was exclusive to the PC version of the first Halo. There's a map I love utterly and completly.