Thats just like, their opinion. To start, doomguy is atleast twice as fast as an average spartan (60mph i think was what someone calculated it as, and spartans are around 35) Secondly, his weapons are far superior (either shotguns make the halo shotgy look like a joke), and he can carry almost 5 times the number of weapons john can (9 in doom 64) As far as strength goes, he carries those weapons along with TONS of ammo The only thing i can give in johns favor is that he can jump, but as of doom 4, doomguy can double jump