Crime levels are high in large cities like Boston, NY, etc. where you have a significant portion of the population being unemployed or making a living doing illegal things. If the cities had enough money to put COPs in the street on foot patrol, or if we could give decent jobs to everybody the general level of crime will go down.

Banning firearms will not solve any problems. Even if all firearms vanish by some sort of magic act, bad people will use 2x4, lead pipe, knives, or who knows what to commit their crime.