Yes, it is. In fact, the Halo Assault Rifle is the mimic of the Marathon 2 assault rifle. It runs about the same basis: Badass Space Marine, stupid and weak AI team mates, bad-mother aliens, hostile environtment, etc. They have similar weapons, IE, Pistol, Assault Rifle, Plasma Pistol, etc. I find Marathon games to be very fun, and actually thought about someone making a more recent version of it, IE, mod for Doom 3 or UT2K4, perhaps...
I usually just wait for these things to come out. They are making a Doom 3 System Shock 2 MOD, where the SS2 game gets put into the Doom 3 engine. Prepare to CRAP YOUR PANTS!
