Dunwich
King in Yellow
Dark Pharoah
Kingsport
Black Goat
High hopes for Innsmouth. As much a cornerstone for Lovecraft as Arkham.
I agree, except that I would move Dark Pharoah to last. It doesn't suck, but the exhibit items are mostly junk and the solo encounters with GOO are broken. I actually like Black Goat a lot, even the blasted herald, but Kingsport fixed the last weak element of the game with the excellent Epic Battle cards. Both the Kingsport GOO and investigators are the strongest yet, and I like the Shan and Moonbeasts because they increase the chance that somebody will get devoured before the end battle.
I actually like the exhibit items and some of the Mythos encounters from CotDP are entertaining. I'll give you the Epic Battle cards - the best part of Kingsport. Otherwise I just don't see much else in there that can't just be thrown into the rest of the set. I've only played with BGotW a handful of times, but I haven't been impressed.
But it also gives to Arkham's largest strength, to steal a phrase, it's toolbox style. Mix and match to your own preferences.
Still have high hoped for Innsmouth after seeing the latest preview:
Here