Final Fantasy X is pure story and you can't say you truly played and beaten this game if you didn't tear up at the ending.
-Seymour has one of the coldest villain theme in the series
-Tidus, Rikku, and Lulu was the squad
-That Auron twist
-The Lady Yunalesca battle was the real deal, one of the only times I've played Final Fantasy games and I died so many deaths! You knew you were in for a fight!
The only FF game that comes close to the level of story and gameplay of FFX in my opinion was Final Fantasy XIII-2.
Noel and Serah's journey was pure Final Fantasy.