I find the map I get tired of the fastest is Bloodtide Coast. It's a pretty enough zone (I know Hawkian in particular likes it) and I love all of the sea life and such, but it feels like all of the content in the zone is either quaggan-related or pirate-related, with a nasty layer of Risen sandwiched between.
I don't care much for Sparkfly either, and those two maps are generally the last ones I'll do. I put off doing Harathi Hinterlands too, but I find that once I start that zone I generally finish it much faster than I remember, so at least it's over quickly (I also like Harathi's humans vs. centaur meta in theory, though it is too cyclic for my tastes).
Kessex never bothers me, mostly because of the variety in the enemies (as Kos mentioned) and the landscape. It's nice and forested on the west side, mountainous on the east, with the lakes breaking up the map nicely. There's the little swampy parts in the SW and NE corners and lots of little towns and such scattered around.
The zones that tend to have one theme (Bloodtide, Sparkfly, the Shiverpeak zones) tend to be the least interesting to me, while those that have a diversity of terrain types (Mount Maelstrom, the Ascalon zones) are at the top of my list. I'm hoping when we do get more 'classic' style zones (instead of the meta-focused zones like Drytop and the Silverwastes) that they push that kind of diversity.
If you're not comfortable doing that let me know and we can work something else out.
