The reason to me, for why "love" means something different to everyone, is because you can never "love" different people in the same way. No two person will ever be loved the same was I love the other, even if I told them both I love them. I think that's why you never really forget people you knew pretty well. They find a way of their own to receive my love and I'll never fully be able to explain how I love them or what it really is...that's how you know you love the person. There may be one certain thing they do that you love and constantly bring up, but that's not why they love you....they love you for you.
And I think this is why sometimes we find a way to "regret" or talk down someone when you find someone new, you begin loving something new that's foreign to you compared to the one you loved ahead of time.
I think this may also why we're quick to stop gaming on the game system, or same string of movies. No two person can be loved in the same way as the other. I know, for myself, why love is so beautiful.