Imperial Germany
I voted "Other" as Imperial Germany after the Great War is my favorite. (I'm sure that people who have seen my posts have already figured that out.) It is, IMHO, entirely plausible for the Central Powers to win or draw, in many possible ways. Depending on the outcome, it can lead in so many directions, some better than OTL, some worse--there's almost infinite variety.
It has the advantage of being close enough to OTL that many things will be similar--no need to invent--and then explain to the reader--whole new cities, cultures, etc., but being far enough downtime to allow that massive variety.
(I also like the High Seas Fleet--too bad the L20 alpha's and the Ersatz Yorks never entered service)
There is also less of a clear cut black and white here than in WWII, so changing the outcome doesn't seem like evil winning out.
Germany can go in any direction from gradual reform to very autocratic, and could be allied or opposed to the USA. I know it's biased some, but I always want to know what the US is up to in any ATL. Imperial German timelines happen at the same time the USA is growing into its full strength--a great complication for any timeline from 1880 on.