I think I came to this conclusion with Final Fantasy.
The best games are: 1, 3, 4, 5 and 9 and Tactics. Anything that has strong "Jobs" identity of Final Fantasy, Fantasy setting, and relevance of the Crystals (Tactics is an exception with the Crystal aspect I think)
Problems I have with other games:
2 is just mechanically awful to play.
6 is alright but its problems lay imo with its magicite system and how it pretty much renders the characters indivdual abilities of their class/jobs as worthless. Who needs Sabin's Blitz and Cyan's Bushido when you can give everyone the Ultima spell and they all work
7 has the same problems as 6 but worse in some ways. And it being 3 characters at a time really sucks, I want to run a party with Cloud, Barret, Tifa, and Cid at the same time.
8 the god awful Junction system, level scaling, and dumb setting and plot.
10. 3 characters again but allivated by swapping mid-battle. Sphere System is a tedious chore to do to level up your characters, but the real killer of this game for me is oh my goodness, the end-game content and activities you can do because imo its the absolute worse of all the games even 7's. It is grindy, it is very luck based, getting the ultimate weapons and overdrive is a pain. Like once you pass the Zanarkand Ruins level the game opens up but the things to do to 100% the game are just not fun to do.
12. I am reserving judgement because I only played the original PS2 version and while I loved it, I still need to play the Zodiac Age version to appreciate the possible improvements of the game.
Haven't played 13 and 15 yet and the MMOs I dont' care for.