Hmmm, I agree.
Well, he IS your best friend, so what do you think... You must know him fairly well, so if you think he would say yes, then go for it, but if you don't think so, then maybe reconsider it, or be prepared to shrug it off if and when you ask. If you have ANY doubts (which you obviously do - you did ask our opinions) it'd be best if you don't just go up to him and ask "Are you gay?", as you'll be immediately screwed if he says no. (not the good one)
Simply, the best advice I can give you is: Expect the worst, and be prepared.