yea. they have the generations generic trio(uxie, mesprit, azelf) the version exclusives(dialga and palkia) the 3 hidden pokemon(darkrai, shaymin and arceus) and the semi-hidden pokemon(manaphy..with phione as a bonus) these 10 are enough.
they added:
heatran, whose seems to have no purpose at all of being a legendary, it would have been better off as a normal pokemon.
regigigas, which was a nice touch and extra insentive to use pal park..but why would the regis have a leader and none of the other trios? i guess you can say lugia or ho-oh are the leaders og moltres, zapdos and articuno..now wouldnt entie, suicune and raikou need leaders as well as uxie, mesprit and azelf? overall, not necessary
cresellia, it is a good idea, it is used to counter darkrais power. not necessary though..arceus could have been used for this purpose
giratina, the ghost/dragon typing is nice, out of the pokemon i just listed giratina will probably have the most usefullness. he might be used as the mascot for the 3rd installment game. if not him, cressilia, one of the 4th generations trio or possibly arceus