In the last couple of years the guy gave a spot on performance as a beloved character with a huge following, went on to be in one of the best blockbusters in years and again get good reviews for it and currently he is getting great reviews for playing freaking Sherlock Holmes.He is not a thespian but he can give a good performance and is very likeable.
Add a couple of hilarious interviews, his famous "PC" meme and his looks that are second to none....it's not that hard.
Playing Superman is a well received Superman movie will just be the icing.