do you think having one of the marvel/dc super hero's protect a city be more effective then cops?

Depends on the superhero and their weakness. Ultimately cops are needed superheroes need vacations as well, and other hobbies or else they become villains too.

that depends are people allowed to beat up people. comics the good guys always beat up the bad people cant do that in real life

We need a good old fashion lynch mob justice...

yes, as soon as we all live in some cartoon city

No, they can't prevent crime on such a wide scale