Terra, Sabin, and uhhh Red XIII are probably up there as some of my favorite ff characters. FF6 in general is one of my favorite games and I like most of the characters in that game, but during gameplay Sabin was consistently one of the most reliable characters and i dunno Terra just has a really fun character arc. Red XIII is good solely because being able to play as a cat is an extremely novel concept and for some reason I find him kind of funny. Ironically though I find Cait Sith absolutely wretched

I only finished 7 and 9 and played around half of 8. But based off my impressions, I'd honestly say the set of Squall and Laguna is surprisingly the best FF protagonist, by a pretty wide margin too, though maybe I just need to replay 9 because Zidane was fucking awesome too. Least favorite was Cloud, though there are still neat things about him. This is also assuming that people like, Vivi, aren't really the main character, even if they are part of the main cast.

Edit: Feel like explaining why. Squall seems like a very believable person to me honestly, there are parts where he lets down his shield or when you sort of get a glimpse into why he is the way he is, and those are brilliant. I can't remember if you can skip it (think you can), but the part where he has to explain the nature of war to the old man near the stadium is just great stuff. Don't know if optional dialogue has ever stuck out like that to me before. Also, Laguna is a huge memelord and reminds me Frank West, which is always a positive in my book. Plus I love the chemistry with his soldier mates. 

I like FF XIII the most. So all of them. I need to restart FF XIII-2 which I was also loving. I lost my data around 40 hours in.

If we're talking about THE main character of each Final Fantasy then...

Favorite:
- Noctis
- Cloud
- Squall

Least favorite:
- Vaan
- Firion
- Bartz

Was doing this about all characters, but alright, so... only main ones:

Top guys:

- Terra
- Cloud
- Zidane
- Cecil

Worst guys:

- Tidus
- Lighting
- Vaan
- Firion

Favorite: Zidane

Least favorite: Vaan - I don't necessarily hate him but almost every other character in the game (which I love, btw) is more relevant than Vaan to the story, Ashe and Basch feel more like the actual protagonists.

Favorite:
Yuna

Worst:
Hope

I root for the bad guy so my favorite main character is Kefka Palazzo!

Naw kidding but he was a great villain.

Best
All the main characters from VI and IX except for Vivi.
Worst all of the main characters from XV...boring characters and a lack of female protagonist!

Favorite - Cloud
Least favorite - Zidane

Didn't played FF XV but Noctis seems pretty boring from the gameplays

Favourite: Squall
Hated: Cloud