Since this is a matter of opinion, I'd prefer it to be called "least favorite".
My 3 least favorite pokemon are...
I'm not a big fan of pokemon I find ugly.
It is new. Therefore, it sucks [/end nostalgia glasses]
Addict let's his nostalgia get in the way of every
opinion. He simply hates
the 4th gen.
I'm sorry, I just felt that was necessarily. But anyway, I just want to note, you don't have to have a reason or justification to dislike a pokemon. It's all a matter of opinion. If you don't like how it looks, you don't like how it looks. Period. If find the three pokemon I listed an eyesore, and ugly, but I can't explain why I think somethings ugly. I could explain why I think a pokemon is cool, like Absol and Swellow, and justify it because they are slender and speedy, like most of my favorites, but then what about Luxray? I like that to, and it isn't slender or speedy.
There was a poll here in Serebii, and almost all users here liked the 5th gen. Like, 98 or 99% of them at least. The reason so many 5th gen pokemon are being posted is because a lot of them were "hit or miss". Vanillite is probably the greatest example. I mean, pokemon has made inanimate objects before, but food? That's crazy. It's a pokemon people either love(and you've got to admit, it's pretty cute) or hate.