Yes,
I have two daughters and my youngest loves power rangers (the pink one of course) she uses sticks as swords to have play fights etc i dont discourage it at all.
and NOW in childcare you are not suppose to discourage imaginative play in anyway, and on a training course i went on recently, these sort of games are actually beneficial to children and apparently even more so to boys, as females we will NEVER fully understand the way males think/feel/learn and evidence shows that boys also learn differently, and are different lets face it, and it shouldnt be discouraged.
Children who play cops and robbers, or cowboys and indians, or power rangers or ben10 etc etc wont grow up with 'issues' because of this or make them violent etc