I would like to continue the topic of superheroes. Next hero I wanted to analyse in terms of matching our safety is Spider-Man (http://marvel.com/characters/54/spider-man).
He’s a genius just like Iron Man, but unlike Iron Man, he uses his intelligence in battle or by improving his costume and gadgets. His not trying to invent new types of weapon but he just wants to help people and protect the city he’s living in (New York). I think people’s safety and incarceration of criminals are Spider-Man’s priorities. And that is why, in my view, it would be nice to have him in our world (also because of his sense of humour ;) ). He could help the police to catch bad guys and not contribute to increasing danger because of his genius inventions.
On the other hand, some people may say that he enforces the law by himself and that is not right, but I think he wouldn’t do any harm to our world. What’s more, he would help us solve the problem of increasing crime rate and terrorism. Of course, not all around the world but maybe in some cities that are thought to be the most vicious.
At the end I have to mention that taking into account the arguments above Spider-Man would be more a caprice nor a need. Someone who may help but is not necessarily needed.