The graphics of Armageddon aren't anything to really drool over, though there are a few aspects that are nice. The character models are smooth and have a lot of detail. For instance, after having your way with a room full of Meat Puppets, Imps and various other hellacious creatures, the blood dripping from Agony (Spawn's Axe) adds a nice effect to the scene before you. Oh yeah, I guess this would be a good time to say that this game is rated Mature, and though it isn't as bad as Manhunt, there is a lot of blood and gore in it.
The levels themselves make use of some good textures, but it tends to be the same thing over and over again -- making them somewhat bland.
The voices in Armageddon are almost perfect. Since the Spawn animated series on HBO (several years ago), I have placed those voices (like Keith David, who also voiced Goliath on Gargoyles) in the roles of these characters. The voices used in Spawn: Armageddon come damn close.