Gears 1.5 (or so).
This game is great fun to play, but is only a slight improvement on the original. Gameplay is similar, as a duck & cover 3rd person shooter. Host lag advantage has been minimized, however actually getting into a multiplayer pub match can take a very, very long time. The game is in desperate need of a patch to solve the slow matchmaking process.
The single player campaign is great fun, reminiscent of the varied and exciting content of the second Halo. Co-op play is seamless -- friends can drop in or out with ease. Controls have not been changed significantly from the original.
The truly wonderful thing about Gears 2 is the achievement tracking. Every time you make progress toward an achievement, an on-screen indicator pops up, letting you know how far you have yet to go before earning the cheevo. This makes for much less frustration and guesswork, especially when you've played the game for a long time, and are wondering when you'll get that difficult achievement.
For people new to the franchise, the learning curve is steep. For people not used to shooters, the learning curve is nigh on unbearable. This game is for the truly addicted, with little middle ground for the casual gamer.
That said, it is also one of the best new shooters around. It must rank up there with Halo 3, Shadowrun, and The Orange Box when considering what is available on the Xbox 360. (My friends would also add CoD 4, or Rainbow Six: Vegas, but those are not my cup of tea.)
Should you rent or purchase?
Here's the deal: if you like shooters, buy it. It is a very good game, with plenty of varied play experience. The matches are fair, the maps abundant, and the bugs are minimal. Also, if you buy, you get bonus maps and other nifty content.
If, however, you are on a limited budget, or you are only a casual shooter, try it first. I have become very tired of waiting to connect to other players and other teams in matchmaking -- a process which often allows me to run to the restroom, have a cigarette, and goof around on the internet between matches, with plenty of time to spare. I also don't think the gameplay has changed dramatically enough between the first and second features. Sure, you can use downed players as 'meat shields,' and all that, but its essence is Gears 1 with some new bells and whistles. Which is fine if you are a devoted fan. For others, like me, I want more out of my Gears 3 and Halo 4 experiences, when they inevitably come out.Read full review