Yes, IMO Marathon was a great game. 2d characters with 3d environments, and you learned the storyline by reading terminals. Can you say, assault rifle with a mounted grenade launcher? :squirrel_evil:
You might not find it fun if you're really used to Halo. Other than that, it's a great game with a good story.
I disagree. I didn't start playing Marathon until after I had been playing Halo for years. You can go to source.bungie.org and download Marathon and Marathon Infinity for free. You can also get Durandal, but the LIVE arcade version is better. Marathon is confusing as hell and sometimes very frustrating, but it's a solid game from it's time. I'd recomend it.