13 gets a lot of unwarranted hate
12 is hot trash. I have no idea what people see in it.
Ivalice is probably the best FF world, if not one of the best worlds in gaming. Plus, a lot of people felt that 13's gameplay consisted of walking down long hallways, and there wasn't much exploration. There was a lot more openness to 12's locations.
The story in 12 isn't as convoluted as 13's, and doesn't depend on the player reading pages and pages of datalogs to understand wtf is going on.
Though people have an irrational hatred towards Vaan and Penelo, 12 has way more likable and interesting characters. Bathier & Basch > Snow & Sazh. Ashe and Lightning are pretty much the same person.
The Gambit system in a lot of ways was a precursor to the Paradigm Shifts, but the latter felt like a dumbed down version of the former. Writing a sort of code to program each ally was more interesting and complex than just choosing a class for them to act out.
Weapon upgrades and shop system in 13 are just terrible...
Now, where did I lie?