For me it’s
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Final Fantasy Tactics
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Final Fantasy VII
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Final Fantasy XI
The three games I keep coming back to in the franchise.
Tactics has the best writing imo as well as gameplay.
Visually speaking VII’s aesthetic and music are peak FF.
And then when it comes to getting lost in the lore and world of a virtual game, I like XI.
Granted all 3 share similar themes like good writing, music, gameplay, etc. but those are my standouts.
How about you?
The final battle slaps too. It was revisited in FFXIV!
https://www.youtube.com/watch?v=GmsSMtswgwA
The best part of the Deltascape raids imo
The best part of the Omega fight is when it sounds like the singer is singing
HOLE 
I found a YouTube link in your comment. Here are links to the same video on alternative frontends that protect your privacy: