I actually like Toliien and Jordan, though I found the last WoT book massively disappointing as well.
I can tolerate W&H's Dragonlance.
Eddings can write well, but he tends to fill his books with a lot of garbage that ruin an otherwise good story. The Belgarion starts off well, but then goes downhill around the third book. The Mallorean is little more than a re-rash of the Belgariad, and while it has its moments, ther's a lot of crap filling it up. The Elenium I think is his best series, he puts in characters that are actually unique, and writes a fairly believable world, though he can't resist putting in scenes that are totally irrelevant. The Tamuli had good moment,s but is loaded down with a lot of crap as well, but at least it's not a total rehash of the series that preceeded it. Then there are the two books about Belgarath and Polgara. They're good in terms of character development, especially the one about Polgara, I had disliked the character before reading that book. However, he rehashes a lot of the backstory in Belgarath, and rehashes the rehasing in Polgara (about half of Polgara at least is a retelling of Belgarath from Polgara's POV).
A lot of game related fiction seems to be crap. I've remember reading some horrible series set in Greyhawk, and a series in the Planescape setting that sucked so badly I couldn't finish it.
I didn't like Le Guin's A Wizard of Earthsea. It was just kind of boring to me, and Le Guin picks terrible names.
The Shadow War trilogy. I found this very disappointing. I like Willow, but this series doesn't even resemble the movie at all. The world is interesting, but the writing is terrible. I think it sort of went against what I expected of the story, and I think it ruined my enjoyment of it.