"The Horde mode is the other great multiplayer addition which makes up for the frustrating host advantage in online play. The idea is simple: take some players, and pit them against a never-ending onslaught of increasingly difficult Locust forces. It's essentially Tower Defense with the Gears of War 2 engine. The action scales up nicely, and once your wave of enemies count rises, things get hard fast. It's addictive, fun, and a great way to enjoy the game with friends once you've already beaten the campaign mode and unlocked all there is to get on that.
In the end, Gears of War 2 is similar to Gears of War, but features some noticeable improvements and additions. The enemy AI is more intelligent, the environments are better designed, the overall presentation is much more epic and cinematic, and Horde mode is one of the most deceptively fun multiplayer modes on the market. Unfortunately, the game suffers from Halo 2 syndrome where the ending is lackluster at best due to the obvious conclusion(s) of major story points being saved for the next title(s). Don't let that put you off, though, because just like Halo 2, Gears of War 2 manages to conquer that and remain a fun, entertaining, and overall memorable game which will be loved and played by fans for years to come, despite its shortcomings."