Impossible to get enough of this game!
The multiplayer is amazing too. Whether you're privately playing over a system link or just on your Xbox with a friend engaging the AI bots in any of the gametypes except the Horde, or if you do grab some buddies and hunker down to confront the Horde, there is plenty of fun all around.
The Horde is easily the hardest part of the game. I have not met anyone yet who can beat it on their own. At best you'll get the Achievement for the first ten levels, but shortly after that you will regret your decision. Even on Casual, the last few levels feel just short of unbeatable if you don't have five experienced players and a definite strategy. My advice: get a torque bow, several boomshields, and mulchers/mortars.
The online multiplayer still has many of its old quirks, especially the infamous Host Shotgun, which allows the host to kill others with greater ease during shotgun duels and dodge the shotgun spread much more easily. Regardless, I still find that the shotgun is stereotypical of many modern games these days, notably Halo 3 where you're screwed if you have any lag at all, and your shotty just happens to be your best friend in Gears.
Overall, Gears 2 is a very pleasing experience that will keep you coming back for more as you seek earning your 100,000 kills for the Seriously 2.0 Achievement. Bring a friend, or four friends, and always remember that explosives are your friend.