To bluntly answer your question....most guys just want sex. So with that in mind, what appears to be a serious relationship, specially at your age, I will bet you any money that at this time next year, that serious bf, will be dating, if not 'doing', another girl. By the way, how do you define a 'serious' relationship'?
Honestly I am 20 yrs old now and still a virgin which is quite uncommon these days... I would say to wait til it means something cause you most like aren't going to be with this guy for the rest of you life and if you are then why not wait for another couple of years!! I mean you both can still do oral and hand pleasures but I wouldn't just give up your virginity like that its pointless!!
I know this probably isn't the answer your looking for and usually I try to avoid giving advice like this to people your age but this is question is just screaming for some older guidance so I hope your parents don't get mad at me for this.
Being a virgin, at your age does it matter to guys? No. It won't matter to most good guys for a long time either.
What do most guys like? Doesn't matter. Never will. IF you decide to risk screwing up your life for a while and decide to have sex with this guy then do it safely and remember that you don't have to do anything you don't want to do or aren't comfortable with. That's true now and it's going to be true when you are 80. If he doesn't like it, oh well, there are plenty more where he came from.
I mean, if you are like most people, you won't even remember this guys name right away 5 years from now. So why should you care what he wants? Do what your comfortable doing (safely) and if he's a good guy and he really likes you he will be fine with that.
Well, that's my lecture for today don't forget to tune in to hear why most people think they made stupid choices when they were teens.
Heres a hint. Because they did! Most people will openly admit to being stupid when they were teens, and that's when they are in their twenties. They have no idea!