Martin has being in the business for a long time and he as put out a myriad of different standalone books, short stories etc etc. Have a look at his
Bibliography in his sub-forum.
Erikson is pretty new to the game and he is pumping out books in the Malazan series pretty fast (A novel per year) considering the quality of the novels, this is astonishing. Its near to a close. I think we'll see great many things other than his current EPIC fantasy.
Agreed on Pratchett, but have to admit his books are very, very good.
Cheers, DeepThought