I've read all the books mentioned so far and out of them I would recommend:
The riftwar saga - easy read, first is the best by far
Malazan books - bit more complicated but very rewarding
Wheel of time - absolutely fantastic for the first 6 then it goes downhill fast but still a must read
The farseer trilogy - my favourite books, all high quality with fantastic characters, her new series is not so good though
Memory, Sorrow and Thorn - very solid fantasy foursome, could have been finished in three perhaps...be warned his other fantasy books are not as good although the otherland books are excellent
I wouldn't recommend the thomas covenant books because as wyrdo says it is impossible to empathise with someone who is unflinchingly miserable.
I'd also avoid works by eddings, gemmel, and brooks as I find them all too badly written to read.
Middling series to read (after the above) include:
Book of Words Trilogy
The First Law Trilogy
The Gentlemen ******* Sequence (not finished)
All other feist books (easy reads but bland characters)
That should be enough for now!
