The new superman film, Man of Steel, won't be released until 14 June 2013, so we can't really decide that until we've seen the film. However, the outlook is good.
Henry Cavill has been a big hit with audiences ever since he appeared in The Count of Monte Cristo in 2002. He could by now have been one of the most famous actors in the world: He was favoured for the role of Edward Cullen in the Twilight films (unfortunately by the time he was free to play the role he was too old for it). He was also a strong contender to play James Bond in Casino Royale (ironically, for this role he was considered too young and it went to Daniel Craig).
But as far as acting ability, looks and charisma go, he should be a really big star and, if the new film is a hit, he probably will be. Though whether he wil be the best ever - better than Christopher Reeve, especially - is something people will no doubt have different opinions about.