Depends on what you mean when you say "best", success wise probably the last one cause he finally killed voldemort, if you're talking about the year with the least amount of potential death then definitely year 3, if you're talking about his happiness then most likely 1 or 3.
He was worried about Voldemort all through that film because of his dreams. All that happened at the end was that his fears were confirmed. And if he wasn’t worried about Voldemort, he was worried about his life being under threat from the Triwizard Tournament.