Is a guy gay if...?

Alright so my best guy friend is kinda weird, I don't want to be mean but I think he might be gay, and so do my other friends. He is just kinda...overly too happy. He is so attractive to so many girls he could get a girlfriend so easy but he doesn't. And today he even told me he would have with his favorite musician (Dave Grohl from Foo Fighters). Does this make him gay? I don't really care, I mean it's cool if he is, but he insists he is not, but I mean, gay ? Opinions please? Please be nice, he is my friend