I've never been to any class where males outnumber females. At my gym (in a London suburb) the largest proportion of males in any class seems to be around 15-20% - and that's on the occasions when, by chance, all the participating guys turn up at the same time! There are about 6-7 guys who come to BodyAttack classes fairly regularly, compared with a hard core of 15-20 women.
The ratio for BodyCombat seems similar (I don't take BC myself but regularly watch the last couple of tracks through the window while I eagerly wait for them to finish so Step or Attack can start!)
BodyStep definitely has the highest F:M ratio, with only a couple of guys regularly braving BS - and often none at all in any given class.
I've tried to encourage the man in my life to give it a shot - and the amount I rave about my classes, particularly Attack, you'd think he'd be keen to find out what the fuss is about! - but he absolutely will not even consider it! He just doesn't consider group exercise classes to be legitimately "manly" or something... it's hard to get him to really say what he doesn't like about the idea, but I definitely get the feeling there's a big dose of fear of making a fool of yourself in front of other people.