Because Army of One just sounds crap.
Initially when I saw Army of Two I thought it looked incredible, graphically impressive and I thought it would be the first game with truly phenomenal and comprehensive co-op AI, so much so that you would think you were palying with a real person. This is where AOT first downfall is.
The AI isn't as disasterous as Conflict: Denied Ops was, but in comparison, the squad mechanics work far better in Call of Duty 4 (there it is again!) The AI is totally thich, it's just not what EA promised, and that's what's disappointing about it. There was no point in the game where I felt the AI was a real person . The command system is very simplistic but good enough but a disloyal compainion leaves you slogging it out a lot of the time whilst he dances pathetically like a moron and falls off ledges. To be honest this games wasn't built for single player, so I'm going to let it off slightly. Naughty Army of Two!
Co op split screen is a lot better, you have some one sitting on the couch next to you and you can discuss tactics and how to best use your Aggro system, which in my opinion is pretty swish. Basically one player shoots the hell at the opposition so all firepower from the enemy is directed at him, so the other one can, in theory, sneak behind the enemy using cover and dodging to fill their backsides full of lead. Sounds simple, but it does get messy. Sometimes, the Aggro will switch if enemies spot a player and this can really send a plan balls up.
This isn't made any easier with a timid cover system, which sees you approaching cover very dashingly as you slide into place, poor crouch position which literally sees your burly guy's big hairy arse up in the air and getting shot at, and, for the first of the game (or until you decently upgrade your weapons) awful recoil. The upgrade system is a lot better. Stick big ass shotguns to you machine gun with barrage shields and grenade launcher and create something that Rambo himself could have given birth to. There isn't much depth within upgrades but you can literally create your own skull shuttering monsters.
However, you never seem to have enough money, from which you earn during missions, to fully pimp out your gear.
Clever features in gameplay include ripping car doors off and using them a shields, back to back gunning situations covering all angles and the fiesty banter between the two soldiers. However, these only happen in specific points within the game unlike how EA described earlier last year. Graphically, it isn't as visually mind blowing as I'd hoped. Character models look great and nearly on par with COD4 (there we go...again) however environments and locations grow bland and all too samey and cliched. There is no particular location that stood out for me.
Gun play is good, despite the minor recoil, and action is ramped up to a maximum, and like Turok, a very manly game. Two players see missions get tactical and action-fuelled and animations are great. You may get injured and die a bit too often though.
Overall, Army of Two is a great shooter but is let down by the enormous promise by EA of human-like AI and scripted events which would have been awesome if they were done in real time any time. A great starting point for a franchise with loads of ideas to work upon but if you're going to buy this game, buy it for the co-op rather than a solid single player experience, the co-op is what really makes it a great game.