Here is the full list of all 12 Gyruss achievements worth 200 gamerscore.
Make it to Neptune without losing a life.
Make it to stage 7 without obtaining any bonus weapons.
Get 12,000 points in the first stage.
Kill all ships on the first 3 bonus levels.
Make it to Uranus.
Make it to Saturn.
Make it to Jupiter
Make it to Mars
Make it to Earth
Obtain a score of 60,000 during an Xbox Live Co-op game.
Obtain a score of 200,000 during an Xbox Live Co-op game.
Win 50 Xbox Live Versus games.