>>50036214none of these are outright bad designs
however
Charizard has nothing interesting about it. It's an orange bipedal dragon with a flame on its tail.
Nor does Pikachu. It's a cartoon mouse with a tail shaped like a lightning bolt.
Umbreon at least is based on something but it fails to be as evocative of its typing as Vaporeon does with all of its details---although so does every other eeveelution.
Gardevoir feels incomplete, in a way its mega-evolution doesn't. Not saying that the mega evolution would have been a better gardevoir than itself; but that this design needed more.
Lucario, I see nothing about it that's praiseworthy other than its head. The rest of its body doesn't make sense in terms of its concept.
Greninja, hate its viability and favoritism however you may, at least was carefully designed to fit its concept in terms of both typing and species. They even managed to make it not primarily bipedal, at least in art like this, giving it just that bit more of a "creature" boost over being like a character.
So all things considered Greninja is technically the best design here and the rest are mediocre. Its popularity proves it and is deserved.