mmm… favorite expansion? hard to say… i enjoyed MoP (cause that’s when i started WoW), and i enjoyed WoD (cause that’s when enhancement shammy was the best imo), legion… legion is probably my favorite, looking back. mw was super fun, i made a bunch of friends, the game felt good to play (though some specs/classes got trashed imo)…
i’m gonna go with legion. or MoP. …or WoD. one of those 3.
Legion is my all-time favorite expansion. I started playing around the time the Nighthold was released. Fell in love with Suramar City, the Nightborne’s story, and Val’sharah. The Nighthold is the only raid that I have AOTC in that I earned myself. Class hall quests and all the amazing raid sets have also made Legion the best legacy content to run. Yep, it’s definitely Legion for me.
Its ok. Sometimes we cant just pick one. When making a breakfast sandwich I can never decide on bacon or sausage so I add both.
My favorite expansion:
Legion because it was the first good one I got to experience since I’m a WoD baby and the garrisons made me wanna quit after a while of loneliness. They did many things right and i stacked up insane amounts of gold through legion table, over 1m or 2m+.
MoP <3 It was when I started playing (during 5.3) and I experienced the launch of 5.4 (Timeless Isle) first hand. Then I got Huolon mount first try, I couldn’t even fly it yet (no rep). Magical place, magical music, magical everything.
Mists of Pandaria will always hold a special place in my Heart.
I started in Cataclysm, and spent most of my time being a noob, just leveling various classes and learning about the world and the Characters.
Pandaria is when I first experienced playing dungeons and raids with my friends and the really special experience behind WoW. Working together with your friends, using abilities and utilities to get through hard content.
Pandaria is when I discovered what wow is really “About” and I’ve been hooked ever since.
ok I can do that
I liked MoP best because I could do what I wanted to do when I wanted to do it. That was the last expansion I felt I could do that.
Skip me for the mount contest as I’m fine that fine and I’m sure someone else will have a better “squeeeeeeee!” moment than I will. 
First of all, none of the expansions I’ve disliked.
My choice would be Vanilla but that’s not an expansion. Not first because it was so well done but because it was just so new to me, starting in July 2006. Everything was so just amazing. I spent about my first 20 minutes just jumping. LOL. I knew nothing about leveling skills, selling via the AH or even upgrading my talents. Fortunately, I started with friends from another game, MechWarrior 3 & 4 and they’d notice things like broken armor or hitting like a wet noodle.
TBC was wonderful. I had new ways to be a complete noob. Our group did dungeons and group stuff and we all looked like we’d geared ourselves from a carnival rummage sale. Much laughter, especially fumbling our way through Zul.
Wrath was my one effort as a progression raider on my mage. Worked my backside off to improve my skills, impoverished myself for gear and enchants and went to work with too few hours of sleep. When the LK went down on our 51st attempted it was just amazing, how it felt do finally do it. We went on to bring down Algalon as well. When it was all done a smiled in satisfaction and swore I’d never do that again. Likewise for the only time in my WoW experience I enjoyed PvP at Wintergrasp. Loved hiding on my Aff Lock and doting up enemy players and defenses.
Cata was a great variety of zones and choices in which zones to level. Friends to level with and to do dungeons. Hated navigating Vashj’ir but it was beautiful and a bold chance on Blizz’s part that generally worked. Started my efforts as an LFR hero as a healer.
Mist was astonishingly beautiful and had a lot of powerful sub-stories that kept my interest. Yu’Lon, the jade serpent was captivating as were the Dread Wastes. I found the mantids fascinating and was surprised at how sad I was when we fought the Klaxxi in SOO. In my head canon we try so hard to talk them down.
Warlords was the first expansion where most of our guild didn’t stick around, especially after the flying debacle. I loved the zones and the stories in them, such as the laughing skull or the desperate stand of the Draenei. I could not get into the meta-story as the bad guys weren’t terribly interesting but each zone had engaging stories and secondary characters. The number of my alts really expanded during this expansion.
Legion is probably my favorite as a package as the zones had distinctive flavors, stories and characters that fit well in the larger overall plot as well. The class halls added a lot of flavor and layers of things to do. Suramar remains my favorite place and where I’d retire. Elisande remains one of my most sympathetic villains while Gul’dan one of the least. I was never fond of Illidan and Xe’ra made me hate him as I could no longer look at him without hearing her voice. ARRG! I was an LFR healer through most of the expansion.
BFA was my first expansion without any guildies and I did most of the dungeons on normal by soloing. I liked the gearing system and miss titan forging very much. The whole N’Zoth was poorly done and I did the cloak to level one and spent gold having the icky stuff removed from gear by the vendor. Lots of great lore, character and stories. All my recent alts have leveled via BFA and I haven’t grown tired of the expansion. Easily a close second to Legion for enjoyment. This is the first expansion where it seemed friendly people were fewer in number and killed any desire to pug, even in LFR.
Shadowlands is doing a good job of letting this casual gear up for world stuff and soloing previous expansion’s dungeons. The stories are not very compelling and few interesting new or old characters have emerged. Basically, I’m playing WoW rather than Shadowlands if that makes any sense. I’m gearing up for my endgame which will be soloing BFA and Argus dungeons and raids. To that end Blizz is giving me a lot of gearing options and I’m very happy with that. Surprisingly, I have a lot of alts with gear moving well into the 220’s. I’m not zerging gearing up as we have a long way to go until 10.0 so no hurry.
Oh, and I continue to find new ways in each expansion to be a noob. Those wonderful “I could have been doing this instead of that? D’OH!”
Well I for one am fully confident that you can squee with the best of 'em. (inner spirit squee’s count too!)
Me tooooooooooo!!!111one 
My favorite expansion is Wrath of the Lich King!
Reason being is that it was when I first began playing, I was enthralled by how massive the world was! The feeling of flying over Grizzly Hills for the first time was magic. The overall atmosphere during that expansion was something I will never forget.
Burning Crusade. The game was on the upswing, and I had a lot of people I knew to play with. It improved on the core game without removing a bunch of stuff. Its the time in the game that got me hooked. Lots of good memories.
My favorite expansion was Mists of Pandaria. This was the first real expansion I played (I started at the end of Cata.) and the first one I really got to experience raiding in.
I really enjoyed the story and how it cumulated with a raid on Orgrimmar.
Wrath of the Lich King was my favorite for bringing a close to the epic story started in Warcraft 3, among other things.
I had a blast playing it with various in-game friends made along the way.
We would run dungeons, pug raids and it always felt like there was something fun to do. I loved being able to gear up how I wanted via badges and crafting even if the profession bonuses were a bit unbalanced.
TBC was a close second though because of all the irl friends playing at the time.
It’s really funny, because when they announced MoP they said they added, like, 300 dailies. And I was giddy. I liked dailies. I still like dailies.
But the Vale. Oh my. And it was smack dab in the middle of progression.
“Thou shalt level seventeen reps to move forward”. Holy…O.O
Yea, just over the top.
Once it was gone, yea, I did a bunch of Vale dailies, did the zone dailies (ToT, TI, etc.) and those other rep dailies, like the August Celestials where you had to do so many of each of a specific quest, but the quests each day were random.
But, yea, early on, overwhelming.
Felt like you “started your day” doing 15 of them and THEN you could “play”. Ugh.
not looking to win a mount; just here to announce my favorite despite most others’ hating it:
MoP.
My favorite expansion was Legion.
It was when I really felt like I came into my own as a raider. My guild started making real pushes into Mythic, the raids were amazing, and I actually had max level characters of every class, just so I could do all the unique class hall content with all of them. Even managed to get enough of them geared to get 12 out of the 36 Challenge mode appearances.
There was just alot to love about Legion in general, more than I could put into a single post, but for me, it was when I really transitioned from a casual to a hardcore player.
Blizzard, 2004:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2005:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2006:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2007:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2008:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2009:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2010:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2011:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2012:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2013:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2014:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2015:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2016:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2017:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2018:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2019:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2020:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players cheer!
Blizzard, 2021:
On Story: “Rule of Cool!”
On Lore: “Epic Do-Over!”
Players: “… Haven’t we seen this before?”
wod. i just loved fishing in the cozy garrison with guildies after raiding blackhand. it also had wonderful graphical updates for player models.
Wrath of the Lich King
The game was so alive then, new players coming in, the content, the dungeons/raids were so much fun. Last expansion that Blizzard got it right!
I’d have to say Legion! I only played WoW as a kid cata through mists then now bfa through shadowlands. So didn’t truly experience Legion but going through it never gets old for me. Some of my favorite zones are there like Suramar and Highmountain, the class halls for me are a fun inclusion that brings more value to my characters class and the story is fun to play through as chaotic as it is!