FFX
Pros:
-mostly solid voice acting
-the Ronso (Kimahri is awesome)
-nice graphics for its time
-interesting idea for a world
-great idea for a battle system
-the expert sphere grid
-switching out characters in battle
-weapon customization
-side-quests involving extra summons and celestial weapons
-the summoning system
-gorgeous music, partly courtesy of my personal favorite - Masashi Hamauzu

Cons:
-I'm not a fan of the plot, characters and the writing overall. This is what kills this game for me. It's like none of the writers of this game understand the concept of subtlety or actual human emotions. Not gonna delve deeper into this, lest I turn this into a snarky hate-fest
-linear as smurf, which is probably not an issue if you like the story
-"religion is evil because it's religion, therefore evil!"
-death is so cheap in this world, why is everyone so afraid of Sin again? Just don't send them, they'll come back just like Seymour and the entire church of Yevon!
-the battle system would have been way more fun if I actually needed to strategize, you know, because everything was too easy here
-smurfin' Tidus
-smurfin' Seymour
-smurfin' Jecht! I mean, not as a human, but as a character. "Let's write him so one-dimensionally abusive that people sympathize with that Meg Ryan dude! Yeah, that's relatable!"
-forced love plot
-bonus: I didn't like that people didn't get the laughing scene was supposed to be awkward. That was one of the few moments that actually felt charming to me.

FFX-2
Pros:
-light and fun - it knows very well it's stupid, none of the delusions of grandeur X clearly had
-the main trio have great chemistry, even if they're a bit flat on their own
-fantaatic battle system
-the job system!!!
-the 1000 words scene - with that one scene and no dialogue whatsoever, this game made me feel so much more for Shuyin and Lenne that the entirety of X made me feel for Todus and Yuna
-non-linearity and missions

Cons:
-way, waaaay too stupid at times
-the music (with a few notable exceptions; ironically, the piano collections to this are superb)
-Shuyin
-Leblanc and her goons
-on that topic - Leblanc's massage scene made me feel very uncomfortable
-too much fanservice - what was the purpose of this? It's like the entire point of this game was to leave you with a few hours wasted and a sticky controller
-the plot makes no sense in the context of the world, while some visible changes were neat, I don't think society would change so much in such a short time
-the clothing designs. What the hell happened to Nooj?
-implied incest!
-the golden ending is too golden for my tastes, but I guess that's just the kinda guy I am.