Now I think it's fair to say that by-and-large, WoW players tend to feel the most affinity and nostalgia towards the expansion in which they started playing. For me that expansion was Wrath of the Lich King.
Over the expansions I've always had this overwhelming feeling of "this was better in Wrath, that was better in Wrath."
Cataclysm compounded this feeling the most (since it was the expansion after the one in which I started) and continued through the Panda beta (during which I unsubscribed, pandas are stupid, shoot me) and all the way through WoD. To my mind nothing could touch those heady days of raiding Ulduar and ICC.
As an aside let me just point out that I am by no means blind to Wrath's flaws. Naxx was lazy, ToC was just horrible and the levelling experience started to vastly improve from Cataclysm onwards.
When Legion was announced I was extremely wary. It seemed as if Blizzard were doing their best to give players everything they ever wanted. Demon Hunters? Done. Illidan returning? Done. Dalaran? Done. A real feeling of class identity? Done.
I was cautiously optimistic. That optimism only grew with the pre-patch and then on Tuesday the expansion dropped during the smoothest launch of an online service that I have ever seen.
Since then (while working a full time job, mind) I've levelled my Demon Hunter to 110, got my professions almost up to max, geared up to 822 and started on Mythic dungeons. I've seen a fair chunk of what 7.0 Legion has to offer and after beating Cordana Felsong on Mythic with my friends last night I think I can say this with some confidence:
Legion is better than Wrath of The Lich King (in my opinion).
And yes, I'm saying that base Legion with no patches is better than the entire lifecycle of Wrath.
I've blasted through the content as fast as I possibly could and I don't feel like I've even scratched the surface. I mean, shit, I even care about PvP!
Aside from the odd technical issue I've had a flawless experience with Legion thus far.
Hats off to Blizzard. I think they done saved Warcraft (for now).