This is turning out to be one of those threads where the OP hasn't actually said or done anything egregious but there are just enough assholes responding on the first page, it leads to a dogpile because that's what's people do for fun here.
OP, I haven't celebrated my birthday since I was 14, I am turning 25 this year, but I understand where you're coming from. It's not about the gifts or the obligatory congratulations, it's about knowing people you care about also care about you, and while I don't want to assume anything about your best friend, I know it must suck to feel forgotten like that and maybe subconsciously have to question the dynamics of your friendship. That can be a scary thing because you obviously are close to this person, so you might not want to confront them because of that and so many other reasons that you think might seem petty, but it's nothing to be ashamed about, no matter how much some here are obviously trying to shame you, it's okay to be bothered by people acting inconsiderately as your best friend did. You have every right to be bothered by something that hurts your feelings and if you want to walk to your best friend about it, I suggest you do.
My two cents.
Also, belated happy birthday.