A lot of this depends on how one's life is going. It is easy and natural to be genuinely happy for others when you are satisfied with your own life. But if I became unemployed and my friend got into Google then yeah...happiness level will be limited. There is a sound evolutionary explanation on why that is so.
This sure plays a big role, I agree. Maybe I would feel some envy in that example, but I would also not let it consume me, and still feel happy for my friend at the same time.
