Looks more like Space Invaders than Galaxia to me.
That really was like space invaders, you know.
If it was Galaxia then the enemy ships would do dive bomb runs.
It could use some things, here are some suggestions.
*Add some animation for the ships explosions.
*Animate the background or use different scenes at each level.
The starfield is kinda boring.
*Make some unique weapons. Guided missiles, big ass cannons, etc.
*Have the enemy do more than move left or right.