As someone who likes GRR Martin's ASOIAF, I have to say I didn't enjoy Robin Hobb's books at all.
For me, the closest in style and content would have to be Joe Abercrombie (First Law Trilogy, Heroes, Best Served Cold, Red Country ), Daniel Abraham ( Long price Quartet & The Dagger and the Coin Quintet ), Glen Cook ( The Black Company ) and some would say R.Scott Bakker, although I personally have not sampled his work.
As someone has already mentioned, there is no-one who is exactly like GRR Martin ; his combination of wit, cynicism, grittiness, historical world building and character development is unique.
You may want to check out Steven Erikson's Malazan series too ; I don't find it absolutely comparable. They have a higher complexity, a certain grittiness ... and there is a more militaristic feel with a healthy dose of high fantasy.