usually, in a gathering where there are a lot of men, i have no problem in striking up a conversation. use it to your advantage. make it your own little personal speed dating. start small talk re the game, introduce yourself, maybe we can get together sometime, get the number and move on to the next. what have u got to lose.
and sometimes, it could be in your facial expression, that can make you unapproachable. smiling a lot never hurt anyone.
i find that most men approach. they feel you out first, to see who you're with (another guy, etc.). they do the same thing we do.
accentuate the positive. also, the good thing about going to a game, you don't have to get all dressed up. you can easily glam up just using accessories with jeans, etc.