I liked it
You wanted suggestions:
-More health on your guy
-Multiple hits to kill stuff
-Multiple levels
-Several lives, not just you die and you're done
-Different weapons on the guy's that you are killing
-You need to be able to shoot the enemy bullets, like on the boss
-Destroyable objests in the background like windows and pots and stuff
-Scoring
Definantly make another - I'll be waiting