Let's see:
Definitely read Steven Erikson's Malazan Book of the Fallen (if you haven't already...i saw it was recommended to you). In my book the best fantasy out there atm. Big, sweeping epic, with unbeatable worldbuilding (ok, Tolkien is still king, but his world is very different than Steven's) and very complex. Don't read it when you're tired/on a train/otherwise distracted
Another fantastic author (and i haven't seen him mentioned in this thread) is Scott R. Bakker and his Prince of Nothing trilogy. It is followed by the Aspect Emperor trilogy (third book not out yet). Also a very well and deeply developed world, with above average prose (imho). But it is really dark at times and very explicit (violence and sex etc. ). So if that is not your cup of tea, then keep away at all cost
Last but not least, i think Michelle West is a very much underrated Author. Her Sun Sword books (6 books) is very well written. Again, deep worldbuilding and very well drawn characters. She writes in a very own voice and she is not what i would call fast paced. If you decide to give her a try, i recommend starting with the Sacred Hunt books (a duology set in the same world as the Sun Sword). While not quite as good as her Sun Sword, they introduce you to the world and its powers. FYI : you can start with the Sun Sword if you want, the author and most fans agree that you don't need the Sacred Hunt books.
I also second Tad Williams' MS&T books and George R. R. Martin's Song of Ice and Fire.