The all time great: Christopher Reeve as Superman. There has never been a better Clark Kent AND Superman played since.
Ryan Reynolds as Deadpool, hopefully they'll let him talk this time.
James Marsden as Cyclops, seriously underated for the fantastic job he did bringing that character to life.
Chris Evans is the all American man, so his Captain America was dead on.
Michael Clark Duncan as Kingpin. When I heard the casting, I was up in arms. In the end, he was the ONLY good thing about that movie.
Same for Heath Ledger's Joker. So many people say that he only got so much hype because he died. I say he's the only one who's ever gotten Joker right on the screen.
Now for some dislikes:
I actually disagree with the choice of Thor. He didn't make me feel like he was a Norse God AT ALL. More like a Norse Teenager with some powers.
As much as I love Ian McKellan as an actor, I actually feel he didn't embody Magneto AT ALL despite people constantly saying he was great.
The entire cast of Daredevil with exception above.
Christian Bale as Batman. Those films did well DESPITE him, not BECAUSE of him. He didn't pull off a convincing Batman OR Bruce Wayne.