Thor! Hemsworth is simply perfect, and his charm is second to none. He was let loose in this film and the results were fantastic. Waititi said his aim was to make his hero likable, and I think Thor accomplished that more than any other hero on this list. I just fell in love with Thor's characterization this time around. His lovable and noble jock personality is spot on for Thor, a near indestructible prince who is a hero by profession. Reminded me of Disney's Hercules, and the recurring "that's what heroes do" line gelled with me. It really succinctly explains the character of Thor without the need for drawn out drama.
Beyond that, his character was the most dynamic of any other hero this year. The way he deals with Loki is the embodiment of how much Thor has grown, and there was a maturity there that just isn't seen in caricatures like Wonder Woman. Life and relationships are complex and ever evolving, and the relationship between the brothers had a depth to it that I suspect will be missed by many who can't look past the humor and levity.
On a more superficial note, he also had the best look, the best action scenes, and the best theme.
Thor is the most likable, most optimistic, most heroic, all while losing more than any other hero on this list. That's why he's simply the best superhero of the year.