The pokemon themselves. They didn't seem like pokemon at all.
They were too awkward and didn't look organic.
Did you like the Hoenn pokemon?
Oh yes? So IYO (In Your Opinion) answer that: What´s a Pokémon?
Hoenn is a great region, few electrics pokémon (I count just one, because one is a pre-evo and the other 2 are pikaclones),
they added great looking Bugs (My second favorite type), and awesome water pokémon (3rd favorite),
the most creative pokémon IMO are there (Mawile, then Lunatone and Solrock),
they broke some stats, like Ninjask´s speed and Slaking´s attack,
it has Castform! a cute and great normal pokémon that is also in the most creative pokémon list, glalie is there too, my favorite Ice pokémon deserves a good place!
5 legendary pokémon, most people don´t like it, but I like! latias and latios are perfect pokémon and they broke that rule of "Legendary Pokémon Don´t Have Gender",
Hoenn introduced the abilities, turning some called "Bad pokémon" useful ones, like dunsparce´s serene grace and the almighty trapper wobbuffet!
Hoenn also Taugh me Braille! I always liked that, but I never looked for it, I searched in the internet some Braille sites, just to catch all the regis (don´t knew about Serebii.net that time, so I translated all the rocks and their strange writting).
Awesome region, awesome pokémon, awesome everything! But like Psychic Politoed said, it´s just my opinion.