You ask yourself three questions:
1) Why do they hate me, and is there is anything I can do about it? Have I offended them in some way and need to make amends? Or do they just not like me because they think no one is good enough for their golden boy (and there's little I can do about that)?
2) Does my boyfriend stand up for me to his family? What is he doing, if anything, to try to change their minds about me? Without his support, your relationship is doomed.
3) If there is nothing my boyfriend or I can do to get them to like me, do I really care? Can I live with it? Can my boyfriend? Can we be happy together without their approval of me? If so, problem solved. If not, it might be time to reassess your relationship and think about moving on, unless you're willing to wait and hope they change their minds about you. You might be waiting a long time, though.
Many relationships thrive without the approval of one or both families. A family's blessing is nice, but not mandatory. If your relationship has gone this long without their approval and you are none the worse for wear, then who cares if they like you?