ssi, Super Space Invaders '91 (World)
majest12, Majestic Twelve - The Space Invaders Part IV (Japan)
Same old story, the aliens are coming, either hide down a hole, or trundle backwards and forwards in a tank trying to shoot the dumb aliens...
This game adds a twist on the gameplay by moving the aliens in different formations, each have different tactics etc. There are lots of nice backdrops and sounds, and your ship can usually stand more than one hit before you die.