Fifth > Third > Fourth > Second > First
I'd agree with this, but Sinnoh is an all around boring region. Third gen is actually my favorite next to fifth, but it gets a lot of hate (for no reason? derp too much water).
Its pretty much a meme to hate Hoenn. I don't think people who say they do actually hate hoenn at all, to be honest.
The reason fourth + second suck so much are:
Sinnoh is a dull region. It had no character at all, and most of it is made up of shitty mountain and cave routes. The gameplay is slow and the evil villains just seemed to be a bit silly. I mean, team plasma isn't serious but they actually got closer to succeeding than any other team, team galactic just sort of flailed about in a few places, summoned a legendary and then failed miserably to do anything with it.
Second gen has the largest amount of shit pokemon. Ledyba, Noctowl, Ledian, Quilfish, Sunkern and Sunflora, Corsola.... I could go on. It did have some true gems like Ursaring, Scizor, Feraligatr, Tyranitar and Espeon/Umbreon, so it does better, in my opinion, than sinnoh. Also, Red.