VII, VIII, I-VI (I played ROMs of all of them, don't remember the order, only finished V at that point though), X, XII, XI, XIII, XIV, XV

Completed I can do more specifically:
VII (2000)
VIII (2000)
V (2000?)
X (idk, but I think it was in 2002 or 2003)
XII (2007)
XIII (2010)
XIV (I wanna say 2011, counting the main story of the very first release of the game as completed)
I (2011)
II (2011)
VI (2012)
IX (2013)
XV (2016)

I'm up to the final dungeon in FFIII as of 2020, and haven't had the motivation to go and finish it off. For FFXI, I'm at L37 or 43 or something around that region and maybe someday I'll touch it again but ehhhhhh. FFIV I got something like what felt as half way, I plan on finishing it after III, eventually, thus completing all the main series.

Spinoffs/Expansions I've completed are: Crisis Core, World of Final Fantasy, FFXIII-2, Lightning Returns, all FFXIV expansions' main stories as they were at time of release. I've also played but not completed FFT, FFTA, FFTA2 (I think? I'm hazy on this one), some FF Dissidia arcade game in Japan which I couldn't read anything for, and uhhhh I think that's all? I forget.