It's not really fair to the others to put Tolkien into the mix with them. It wins outright (or should win, at least).
Here's my view of what I think of the series...
Shannara - The first one in the series really felt like bad fan fiction to me. It was almost connect-the-dots kinda writing. The writing gradually got better. I think I stopped at the point where Walker Boh becomes the new Druid. I gave up on it appealing to me.
Dragonlance - This initially appealed to me greatly. New world and everything. But gradually the Raistlin adoration got to me. I think I read two of the trilogies. By the end of the second trilogy I felt like Yul Brynner in The Ten Commandments - "Moses' God is God"
. I gave up at that point. The work by the authors was done well. The first trilogy was pretty good.
Forgotten Realms - I *assume* that this is the same as the Drizz't books. I read about 7 or so of the books. The first one (from a chronological point of view - showing Drizz't's origins) was probably the best one. I grew tired of the repetitive nature of the stories. The dwarfs are particularly boring to me. And whatsername falling for Drizz't was the last straw. I really liked the fact that there are Gods and I especially thought Lolth was a fascinating creation. I tired of the story when it reverted into a Drizzt vs. Artemis Entreri thing and the Drizzt adoration almost became self-congratulatory.
Sword of Truth - I really found the second book (I think the second) with it's long drawn out torture sequence to be so weird and out there that I didn't read this any further.
Xanth - Is this the same as Dragonriders of Pern? Not sure. If so, I didn't quite like any of the stories in this - never really caught my imagination. {Edit: Ruaidhri clarified that Xanth is different from Dragonriders of Pern }
The rest I haven't read.
Of the remaining non-LOTR, I would rank them as
1. Dragonlance
2. Forgotten Realms (Drizzt)
3. Shannara
4. Sword of Truth
I would recommend Tad Williams' Memory, Sorrow and Thorn trilogy and also his Shadowmarch series.
Another shoutout to Jonathan Stroud's The Bartimaeus Trilogy.
I am somewhat partial to Eoin Colfer's Artemis Fowl series too.
And talking about the world itself - I really recommend both Tad Williams and Jonathan Stroud for their world-building piece - with props going to Tad. He does an awesome job of creating the world. Jonathan's idea of Djinns (Genies) is (to me) a pretty unique take on Fantasy (bring it closer to The Arabian Nights world of Genies which to me is somewhat less exploited in modern fantasy literature). However, Jonathan sticks to the story itself. So Tad easily wins on the world-building side.
