Some of them, like Mawile, Ampharos, Kangaskhan, Pinsir, Charizard and Absols Mega evolutions made them Pokemon better. (Though some of them could have been proper evolutions.) Then they give Megas to things like Garchomp, Tyranitar, and Gengar that were already good, and just make them OP. :/

There are lots of other things that would kill for a Mega Evolution. Like Wigglytuff. xD