Why was Esav so angry at yaakov for stealing the bracha even though it was over 20 years since he saw him?
Because he had made a fool of himself by being unable to control his hunger and by not taking seriously Jacob's proposal for the exchange of his precious firstborn right for a bowl of lentel soup.– Ben MasadaDec 17, 2010 at 18:58
He felt like the bracha totally determined his destiny and that of his offspring forever.
If you look at what Yaakov sent him -- a specific number of male and female animals. 200 female sheep + 20 male sheep could be: 220 sheep that you use up, or a breeding supply that you can use to produce lots more. What you make of it is up to you.
Esav felt like "that's it I lost the bracha my life is ruined and it's all Yaakov's fault"; Yaakov is replying "you're still in control of your life, and it's up to you to decide what to make of it."
I think that Esav did not accept Yaakov's gift of those sheep, because he was afraid of another foul play. So, he found much more prudent to leave him alone and get lost. It means he had got a little wiser during those 20 years of absence.– Ben MasadaDec 17, 2010 at 19:03
Because the eyes make the heart fonder. For 20 years Esav only remembered that he had been cheated by his brother. At seeing him after all those years, his mind had been given the chance to go through all the good time they had spent together. His brotherly love was back again.