That's a pretty shallow vision of "masculinity." Being a man = making lots of money, fighting, and treating women like sexual objects?
I actually think Yakuza's vision of masculinity is deeper than that. Both the protagonists have very admirable traits -- e.g., courage, integrity, strong ethical code, compassion, loyalty, sacrifice, etc.. (As opposed to GTA, where everyone is just an asshole.)
As for the approach to sex, I don't think it's "masculine." I think "juvenile" probably describes it better -- at least some of it. But like the other guy said, you have to recognize that it's being played for humor, and the writing is good. I don't mind it. I take it in the spirit intended. It just stands out as different, that's all.