The movie is touching and his performance is sensitive and restrained, so he deserved to win the Golden Globe for Manchester By The Sea. Performances are always the result of a collaboration between the actor and director, and even marginal actors can deliver exceptional performances from time to time. Besides, the winning of an award is insignificant in terms of measuring talent and many noteworthy performances go unnoticed due to limited releases and poor box office performance.
Unless Casey Affleck bribed the judges into voting for him, he won his Golden Globe fair and square. This was based on his acting performance in his latest movie - Manchester by the Sea. This is proof that Casey Affleck is a good enough actor to win a Golden Globe.
I believe that anybody is a good enough actor to win a Golden Globe, it should not be based on their popularity as an actor, or the amount of films they have been in. The Golden Globes are awarded after much deliberation by a panel, who will have taken all of the acting skills into account and therefore anybody who wins one is deserving.
Yes, Casey Affleck is a good enough actor to win a Golden Globe because he has experience as both an actor and a director, and he made his character interesting. Some people don't know that Affleck has a long acting career. As a child he appeared on PBS. He has learned a lot during his long career.