If it were me I'd beef up the action and maybe add in a little more blood. I don't want any of that gorey stuff though. I hate that.
Maybe make Eggman's plot devices a little more ingenious and have him manipulate some of the city folk into joining his side. I'd also love to see the military get more involved in the whole 'Strange creatures are here from another world and we must capture them because they look odd and wear gloves for no reason' thing a lot more.