Well, it depends on how strict you are on your definition of SciFI. I personally think there's a distinct difference between Sci Fi and Fantasy. Mostly I lean towards Fantasy, but here are some I have read:
Margeret Weis and Tracy Hicks have a few series that are good. Of course there is the Dragonlance series. There's also the Sovereign Stone series that is quite good. Both of these are fantasy.
Weis has a few on her own. The Darksword series is very good, and very sci fi. Also, she has another series called the Death Gate Cycle that leans a lot more toward sci-fi.
Robert Jordan's "Conan the Barbarian" series of books are very good, with little of the political silliness that has expanded his WoT series to 11 books and counting. Wot is short for Wheel of Time. It's more fantasy at face value, but if you consider the implications of the actual wheel of time and how it works, I guess it is science at its core, or perhaps theology.
Terry Goodkind's, 'Sword of Truth' series is pretty good, more fantasy again, but I warn you now there is a lot of dark and sexual content that some find hard to overlook. Also, the books seem to be up and down. Some are very good, even excellent, others are bad. Soul of the Fire reads like smut.
Terry Brooks is ok, although myself I only like his Shannara books and Landover books, but even his newer Shannara books I didn't like much. He also did one Star Wars novel that was alright. I consider his books to be a lighter read. He tends to gloss over a lot of things. His Knight of the Word series is modern fantasy. His Shannara books are fantasy on the surface, but sci fi in their core, because it is a post apocolyptic earth.
Forgotten Realms is very very similar to Dungeons and Dragons. Reads very similar also. Anything by R.A. Salvatore is quite good, although he does have his flaws. I really thought the Crimson Shadow series was quite good as well. Again these are fantasy.
Deborah Chester wrote a trilogy called the Ring, the Sword, and the Chalice that I read recently that was very very good. This is fantasy as well.
Tad Williams is an awesome author, whether you like his medieval stuff (Memory, Sorrow, and Thorn series), or his sci-fi stuff (The Otherland series is VERY good if you like this kinds of books).
C.S. Friedman is good, but more sci-fi. The Coldfire Trilogy, is another "after earth" type sci fi that reads a bit like fantasy.
Lawrence Watts has a few stand alone books I've read that are good, like Touched by God, but I REALLY liked the Misenchanted Sword. These are most definitely fantasy, with quite a bit of humor.
David Duncan's "King's Blades" books are excellent, although they are told from different perspectives and sometimes the books seem to contradict one another. Again, fantasy.
John Marco's books are also good, but not as well written, I didn't think. These definitely have sci fi elements. It's kind've a mixture of medieval warfare and technology.
Fred Saberhagen's books are ok, but nothing particularly great. His book of swords and the series that go along with the same vein are pretty interesting and creative. His "Faces of the Gods" series are all very creative as well, with a slight sci-fi twist.
David Eddings books are all fantasy. They are pretty good, but after you read one series, the rest all read pretty much the same. The guy even wrote the same story twice, just told it from a different perspective and sold it twice (Belgarath the Sorceror, Polgara the Sorceress). I personally liked all his books until he wrote the "Elder Gods" series. At this point, it became very obvious that he wasn't going to deviate from his original formula and his stories are all way too similar. The guy is a financial gold mine the way he can keep selling the same story over and over again, but not that great a story teller. Too close minded. Read his Riven Codex if you want to hear his POV. He tells the same story on purpose, and feels like he is stooping to a lower level having to write fantasy, instead of writing in high english or whatever the hell his preference is.
I'm sure I've read others, but I can't recall at the moment.
Mathius