It depends on what the pokemon are like i surpose. I guess in Hoenn they chose Treeko for Ash as it was the most manly starter cus the others look a bit girly, while Torchick is more girly then Mudkip, so they gave it to May.
As Ash had a fully evolved fire and grass type, i expect they wanted to give Ash the water starter, but it was the only one girly enough for Dawn, and although Ash would have looked cool with Empoleon, him with Piplup could've taken away the heroic figure they're trying to asociate Ash with. So instead they gave him both the fire AND the grass type.
What they should've done is had Ash evolve Totodile all the way in Johto, then they wouldnt be in this mess, but hopefully the next water type wont be an obvious girly candidate, and Ash will get his water powerhouse.