The reason you have great sex with your boyfriend and maybe good sex with others is because you're young. What the fuck does this have to do with anything? You have absolutely no idea what you like, what makes you tick, what turns you on, makes you hot, and makes you cum. Your boyfriend, with the constant sex, has somewhat learned what you like (good thing, because most guys fail at this, hard) However, other guys don't know you and because you don't know you either, it's not as great as it could be.