i usualy dont give high marks on things like this.
But honestly i think you have some badass potential and i want more. i would suggest laying off the gradients for a while and shading it in yourself (it gives it a gritty but professional look thats perfect for this type of game). and try to figure out how to have the enemies fight back. (i honestly dont know i just animate i dont make games)i loved the multiple guns. if you can make them selectable that would be just perfect. make something with better animation (if you cant draw well yourself just get somone to help (hell id be glad to))honestly you have some serious capability. so please make another with perhaps a better storyline and better animation. cause the game flow was good.(sorry to rant like a pro (which im not) but these are just some healthy tips others gave me)