Personally, my favourite continent is Pandaria ( I liked MoP before it ended ). It was easy on the eyes, compared to what we have now. The landscape there was pretty diverse, and combined with the music it felt like the game still had that touch to it.
Northrend is probably my second favourite. I remember asking my brother around 8 years ago - "What do people like so much about a frozen wasteland full of walking corpses?". But then I saw places like the Howling Fjord and Grizzly Hills.
Unlike Legion - the same thing over and over. Mac'Aree barely saved Argus for me. I am aware this is a Burning Legion-based expansion, but the demon fatigue/fel started at the end of WoD and hasn't ended. Thankfully it won't last forever.