There is the already stated points of active reload, great Co-op play, an above average story & voice acting for a FPS, EXCELLENT cover system (except it would be nice to be able to jump WITHOUT going into cover). To add...
1.) Chainsaw gun! Everyone is just jelous they didn't do it first.
2.) No one said anything about the simplistic squad control (regroup, attack, defend?). Although not the most comprehensive command list it still is a welcome addiction in a genre that would usually not incorporate it. Plus I really like how seamless it is to use and they could really expand on this feature in the future.
3.) Not necessarily innovative but, like Halo did, they have a good managment of weapons, specifically only being able to carry a certain amount. Many games in the genre just like to let you carry as many guns as possible which can actually take away from the experience and tactics the gamer takes. I just think it was VERY well balanced.
4.) Back to the weapons...seeing the weapons on the players back. I know Halo 3 will be incorporating this but I'm not sure how many other good games have done this, let alone console games. I think this is something that is at least very new to the genre if not innovative.
5.) Curb Stomp! Another genius idea.
I could go on and on about this game. Some things are right out there for you to see but some others are rather hidden in the gameplay and are harder to really explain. Some things might be innovative and others might not. But the fact is that no matter if the game is full with "innovation" or not it is still one of the greatest games I've played in a LONG time. When did a game have to be innovative to be great? EA needs to worry less about people being innovative and actually make a game thats good at doing the basics. IMO Gears of War does have some innovation (although it's not going to compete with nintendo) but more importantly it does everything that it should do RIGHT. Not many games do so many basic things that define the genre right all at once.