That's exactly my point though. I'm not sure if this assumption that a majority of men prefers male protagonists holds true.
It's not really the same thing, but look at the amount of guys playing female characters in other video games. The usual commentary is something along the lines of "I prefer looking at a hot girl while playing".
I'm not sure if the assumption of "self insert" is really accurate in this case... Actually, it would probably be interesting to have a survey done on f95zone or something.