I don't think there are a lot of people who identify so strongly with one company that they automatically prefer that company's characters. Sure, there are some, but most "Marvel fans" just happen to be people who read and like more Marvel comics than DC comics.
So I am a "Marvel fan" in that I tend to be more interested in Marvel comics and Marvel characters - but I'm not going to pick the Nova Corps over the Green Lantern Corps or Black Cat over Catwoman; it's no contest which is the better character, even overlooking which one came first.