ONI was my first. Always drooled at pics in PC Gamer of Marathon and Myth, but at the time never had a PC capable of running them. Forgot all about them once I got a PC built for Unreal Tournament and Diablo 2. Halo was the first that really absorbed me, even as a PC FPS gamer. The story, setting, Cortana, music cues, AI, etc just sucked me in. Played till Halo 3, and now I am patiently waiting for Destiny!