Here is the full list of all 12 Xevious achievements worth 200 gamerscore. It takes around 5-6 hours to unlock all of the achievements on Xbox 360.
Destroy 500 air-based enemies!
Score 100,000 points.
Destroy 100 ground-based enemies!
Destroy Andor Genesis!
Score 40,000 points.
Reveal a Special Flag!
Reveal 5 Sol Citadels!
Reveal 3 Sol Citadels!
Destroy a Sol Citadel!
Reveal a Sol Citadel!
Destroy 30 ground-based enemies!
Destroy 100 air-based enemies!