EXCELLENT

Terry Pratchett
Gene Wolfe
Robert Holdstock
Iain M. Banks (OK, so he's SF, so sue me, he's still bloody excellent! *g*)
Mervyn Peake (with the caveat of very little output)
Keith Roberts (for one absolutely beautiful book of linked short stories titled 'Pavane')
Fritz Leiber (when reading Fafhrd & Mouser - remember they were originally related, but standalone, short stories & treat 'em as such! They're not cohesive novels, they were never meant to be!)

DECENT

Andre Norton
Michael Scott Rohan
Louise Cooper
Patricia McKillip
Michael Moorcock (strong on imagery, short on plot, as a rule)
C.S.Lewis (can reasonably claim to be one of the founding fathers of Fantasy)
Roger Zelazny (Lord of Light is actually SF, guys! *g* I don't entirely buy the "too complex" argument on Amber, either. But like Wolfe he's a crossover F/SF author, for sure)
Ray Bradbury (no, seriously - he's written a few things that are... weird... to classify, more F than SF (Something Wicked This Way Comes, for a start) & are pure class)
Ursula le Guin (for Earthsea alone)

READABLE

Guy Gavriel Kay
Peter Morwood
Harry Turtledove
David Gemmill (too much of his stuff reads like a "history of battle tactics" manual, or stock adaptation of mythology...)

DODGY
Eddings (engaging, but lame - characters are cardboard cutouts, repetitive plot devices, & no atmosphere whatsoever as cardboard characters talk modern & act modern throughout...)
Jordan, Feist, Donaldson (all of these seem to have been compared to "Tolkien at his best", all of them seem (to me) to have been rated on their verbiage, rather than ability)

CRAP
Terry Brooks (started out with a blatant JRRT rip-off, 'nuff said)
Piers Anthony (cliched, moralistic, sanitized s**** - everthing's worked out by inane puzzles & no-one ever gets hurt!)

Ignoring quite a few authors on the way, but just my twopenn'orth... *g*