Westeros ftw, it is far my favourite world ever.
If we talk about steampunk and SF I would say also the Iron Kingdoms RPG world - steampunk. And Star Wars world - SF.
For me, it has to be the Iron Kingdoms.
If a map of the world makes you look closely for interesting spots (or "untreated areas") for inspiration, if you look up current and ancient sites of events and how close/far away they are from other contemporary events - I think that is a very dead giveaway.
I like quite a lot of fantasy worlds but one of my favourites is golarion
Wheel of Time series
My favorite would be Robin Hobbs world (Farseers and Liveships) and Joe Abercrombies setting is cool too :) ... also enjoyed the Germanic Warhammer Fantasy Roleplaying setting :)
Pullman's World of "The golden Compass"
Deep China of "The Promisse"
and i love the Phantasy Star universe with all worlds of Motavia, Parma and Dezolis.