Halo 3 hands down without question. The multiplayer got me hooked and as for campaign I enjoyed the ending. I never have and probably never will play a game that was so good like Halo 3 that made me come back for more each day to keep playing it. Multiplayer games these days I can play for a bit and then take long breaks from. Halo 3 there were no breaks and it was the only game in my disc tray for years.