I liked Zero. It was fun to get medals and to open the alternate paths. The controls were easy to get used to. The only one I didnt like was the side view cockpit thing. I think an option for normal controls would have been good, but I really didnt have a problem.
I liked Adventure when it came out, but as time went on, I saw the seams coming apart towards the late game, where areas are emptier, less developed, and kind of ugly. The game clearly wasnt finished.
Assault had a lot of high points, but besides medal hunting, the game was empty. It had multiplayer, but who was gonna play that game with you? This was peak Halo time.
Never played Command.
ORAS secret base: http://imgur.com/V9nAVrd
3DS friend code: 0173-1465-1236