If you're looking to replicate a comic book / superhero series sort of reality, the ratio should actually be in favor of the villains. Every significant comic hero tends to have an entire rogue's gallery of enemies, after all. Also, it is more heroic to overcome long odds, and more villainous to gang up on a heroine or to strike one after another.
Ultimately, the ratio of one side vs. the other is up to you, but I thought I'd offer an alternative concept to what's mentioned above. Regardless, I hope you are able to get this accomplished... it's an intriguing scenario.
-JM