Unlike Gears 1, the achievements in Gears 2 seem much more reasonable. You won't see people screwing up ranked matches because they're trying to get enough pistol kills for the points this time around. The achievements for public games are the mildest of the bunch. There are certainly some that will take time, though. Overall, the achievements in the game are pretty satisfying to earn and, if you're like me, you'll end up with close to half of them just by playing the game normally.
Also, some of the achievements are built in such a way that you can get them when playing splitscreen against a non-existent opponent. And you could technically get that "play 1999 rounds of multiplayer" achievement by leaving your console on for a night... maybe two nights. To be clear, I don't recommend that. But hey, I'm also the same guy that left GRAW on overnight for the exact same reason, so maybe I shouldn't tell you how to live your lives.
Check out the achievement guide over in our bitchin' guides section. Notice that I haven't built a guide that details the locations of all the hidden collectibles. I put that challenge out to you. Which one of you will be the first with a great, image-filled guide for that?