Just to play Devil's advocate: It's not like Ivysaur is that much better than Bulbasaur. I mean hell, they look extremely similar.
As much as I like Bulbasaur's evolutionary line, I have to agree. If Ash's Bulbasaur had evolved here I wouldn't have minded, tho Ivysaur looks kind of plain and not much different than Bulbasaur hee hee.