I for sure have a very unique ranking 
- TBC
- WOD
- BFA
- SL
- WOTLK
- MOP
- Cata
- DF
- Legion
TBC had the best raid and group content I ever played in an MMO. The idea of being attuned to run the next dungeon or raid, was amazing and kept guilds together. I still wear all my titles with proud.
WOD had a housing like system that I miss since then, I never understood the hate for this expansion, we had so much to do there, I still have not finished it all.
BFA was story wise really great, I had a lot of fun with the quests and story, I also felt the raids were done nicely and crafting had a purpose. To unlock new recipes over time felt worth my time and not wasted.
SL had Torghast, the first solo dungeon experience at WOW. The raids were in my opinion on the better side, especially with Sylvanas. The open world content was fun to do, but I never enjoyed the final content patch with these “gismo” like people.
WOTLK is the best for some, but for me it was a tad annoying as it introduced various raid sizes and this killed my casual guild. It was so hard to get 25 together, if 10 were sufficent and so it happened that the best of us went in one group and did LK HC, while the other part could not even get a raid on normal clear.
Many of my friends from TBC and Vanilla left WOW out of frustration. I see WOTLK as the expansion that killed guilds, so despite the great scenery I can not rate it higher. I also feel that the dungeon finder was a bad move, but the biggest issue will always be the raid modes, normal - hc, 10 and 25… it´s nonsense.
MOP, just not my cup of tea. The tillers were fun tho. but raid wise this may be the worst expansion I played. A lot of content seemed to be a repeat and just like in WOTLK, we were doing daily quests all the time just to unlock things that were not equal to raid gear.
I also never enjoyed the 3 player scenario thing, as it seperated the playerbase even further.
Cata on release was a bomb, I played the first raid tier with my new guild and it was super challanging. Then Blizz removed the difficulty and the expansion became a walk in the park.
The quest zones were not my cup of tea at all, I would rate them as the second worst I guess.
DF, I hate dragon riding and I admit it´s a skill issue, but I also miss my druid flight form. To design an entire expansion around such a hard to master ability was in my opinion a mistake. You can also see that Blizz tried to prove something with this expansion and I just don´t feel woke enough to understand why.
Legion had a design error in my books and that were the space ships. Too much warping through time and space for me, I felt the dungeons were incredible boring, the quest zones not my cup of tea either. The addicts were fun to play with, but it was just a single dungeon and layout with our followers and they pretty much only served us in bringing the treasure to some other addict.
Needless to say, not all dungeons were available in the DF, which is when Blizz started to lock story and content behind premades.
I know, it´s a weird list but that is how I feel.