FFX-2 was much better than FFX. FFXIII-2 was just as good as FFXIII.
A sequel based purely on fanservice was much better than the original?
The original's story was a complete ripoff of Grandia 2 with a biblical theme (i.e. main enemy is called "Sin", summoners sacrifice themselves for the people like Jesus, science aka machina is forbidden and evil by the church, etc.)
The characters were by in large terrible. Tidus was an awful protagonist that looked like a reject from an Abercrombie and Fitch catalog, Wakka was a racial stereotype just not as bad as Barrett, Yuna was about as interesting as a rock until she actually was free to have a life in X-2 and develop a personality errr, I mean she became a slut according to most, etc. etc.
Most people hated Blitzball (though I spent more time on that than the game itself, as I loved it). I got all the celestial weapons, crafted better weapons than the celestial weapons, etc. I 100%ed that game and put a lot of time into it. But I was 12 or 13 and didn't really notice all its flaws until I went back and played it again later. People need to stop putting that game on a pedestal. It's even more overrated than 7 IMO, because 7 was actually good; you just hear about it so much you want to hate it.
Generally there are a lot of bad ones, but Suikoden II, Shadow Hearts II, and Star Ocean: The Second Story disprove that theory. There are also plenty of Japan-only examples too, like Tengai Makyou II: Manji Maru and The Legend of Xanadu II. Actually, I think Breath of Fire II might be another one. Hell, what am I saying, there's tons of great sequels.
Aside from art style Ar Tonelico 2 made 1 look like crap. ATQ on the other hand not so much...
There was definitely too much fan service in ATQ, but with that aside I did like some of the characters, the story, and above all the OST that's what sets it apart (imo of course)
Atelier Iris 2 (although I loved the first, the second was simply better, 3 not so much) Golden Sun 2 SMT: Nocturne Etrian Odyssey 2,3,4 Grandia 2 I enjoyed the first one, but I liked the story, and characters of 2 a little more.
If you're going to throw words around at least know their meaning. Case and point for GFaqs. Troll, and Weeaboo.