This XBLA game is pretty fun, but here's an actual retail copy with all three games on a single disc. I think this might be a cheaper route since it maybe around $29.99. No word if a PS3 or PC Trilogy will come.
http://www.joystiq.com/2011/02/26/alien-breed-trilogy-headed-to-retail-on-xbox-360-march-18/
http://www.joystiq.com/2011/02/26/alien-breed-trilogy-headed-to-retail-on-xbox-360-march-18/
