GoW2 succeeds in making the first title obsolete.
Gameplay - Part of what makes Gears of War 2 so addicting is the engine itself. I haven't seen such a beautifully crafted game engine since Half-Life 2. Everything just runs the way it should and the game is just fun. It actually feels like you're doing what your character is doing in the game.
Controls - The game controls very well. It takes a little getting used to just as in the first, but its improved and it works very well once you understand it.
Sound - No complaints here. The sound is very good and immerses you into the action.
Story - There's enough story to keep you entertained, but it's not too much where you're like "Just shut up I want to shoot some stuff!"
Replay Value - Thanks to the game engine and the horde mode, this game actually has quite a lot of replay value for an action game. Plus the multiplayer is always interesting to kill a few hours.
Overall - Gears of War 2 is a gem of an action game. And anyone slightly interested in action or intense combat should look into Gears of War 2. If you're a huge action fan play Gears of War 2 NOW!