People's go-to rationale for not liking Superman is that he's "too good" or a "boy scout" or "faces no challenges," and that this is somehow unrealistic or boring. Now, I don't care whether you like Superman or not, but I want to address some of these criticisms by way of comparison. Superman is awesome in a different way than the Avengers are awesome (I'm going to use the Avengers as counterpoint because they are a) fundamentally different than Superman; b) a group of heroes allowing me to compare Superman to not just one hero, but instead six; and c) they're big time right now).
The Avengers are cynical, petty, egomaniacal, and in the case of Captain America, deferential to authority. In this way they are "realistic," and I feel like audiences enjoy the in-group tension and squabbles because prideful and hyper-talented people tend to do that kind of stuff. Superman is none of those things. He is moral and humble, but compared to Captain America he caters to the needs of the people (as he perceives them--but he has help from a cross-section of society: Lois, Martha, etc.) and not always to the government. He lives amongst the people, which is something none of the Avengers do. Superman is not realistic, but he's what heroes SHOULD be, whether those heroes are of the super or ordinary variety. He has no interest in being a god, a celebrity, a millionaire, or even a hero really: all he wants is to protect the people he cares about, ALL people, when they face a challenge they cannot handle on their own. Superman is what we want heroes and governments to be, while Avengers are what heroes and governments are. I think that makes Superman awesome.
Now the argument about him being boring is different. We are cultured to be attracted to flaws (personality flaws only, unfortunately, since we live in an age of advertising). Superman takes the high ground, sure, and is pretty much morally flawless, but what MAN OF STEEL touches on is how difficult that can be for him. He's not a "boy scout" because he's an all-powerful entity. He's a "boy scout" because he was raised really well by his parents. But he lives in the same world that we do and is prone to the same temptations that we face. I would argue that witnessing that struggle is all the more fascinating because we finally see somebody overcome those temptations for once. For the past couple decades (at least) we've seen so many anti-heroes that it has become exhausting, expected, and in the case of new characters a bit lazy. It's nice to see somebody not only fight his inner demons, but actually come out on top. Go Superman. And go MAN OF STEEL for breaching the tough nut that is Superman.