Heath Ledger, Matt Smith, Ben Affleck and now Game of Thrones. The internet continues to make snap decisions about their opinions – and they continue to be wrong. Health Ledger was universally derided when his casting as The Joker was announced. He went on to produce what was/is, without question, the definitive portrayal of The Joker in the history of the character. His performance is so untouchable that EVERYONE ELSE is in his dust. I will concede, Mark Hamill is the closest he has to an equal in terms of performance, but (as yet) has only performed as the voice of the character.
Matt Smith, when originally revealed as the eleventh Doctor, again, there was near universal derision. But he was beloved by almost the entire fandom by the end of his first episode.