here are some ideas
well dude, to tell you the truth... it wasn't THAT BAD, considering it was your first. but, hey, you can always do better, by making it longer, a wee bit more realistic (maybe some blood), and of course there's always the surprise element. i'll give you an idea: if you plan to do a remake, or maybe a series (who knows???) I suggest you put, like, after some fighting, an option to choose who wins and stuff, and even maybe some : "extra endings" or even a purple guy coming out of nowhere. Is up to you. Just remember, try to be as original as you can.
smell ya later dude