Here are some games that I think are the easiest games to get every achievement from. Easy easy gamerscore.

Avatar: TLA: TBE

1000G Total

5 Achievements

This is the easiest 1000 Gamerscore, ever. All you have to do it start the first mission and get your hit counter up to 50 by pressing the ‘B’ button. Thats it! All 1000G unlocked.

TMNT

1000G Total

23 Achievements

To get all the achievements on this game all you have to do is complete it, and its really easy because its a kiddies game. You will have to play 1 level again to get a gold coin and thats it.

NBA 2k6

1000G Total

5 Achievements

Really fast game, simply set your sliders to full in the game options so you get a large advantage over the other teams and do as the achievement says.

Eragon

1000G Total (2000 if you buy both versions)

37 Achievements

This game is easy, complete it on normal and hard whilst collecting all the secret eggs and the 1000Gs are yours.

More comming soon…

Borderlands… it is actually a pretty good game. Reminds me of Fallout 3, but in a Street Fighter IV style.

At the moment on this game there are so many bugs and glitches. Its annoying. Here is the achievement that glitched out for me:
Pandora-dog Millionaire (50G) – Earn $1,000,000.

Apparently starting the game again will fix the glitch and the achievemtn will unlock. Yay!