I suppose many, if not all, fantasy authors owe something to Tolkein. Stupid thing for me to say really because even D&D owes Tolkein a lot.
I suppose what I mean is that if someone did a LOTR mod then it wouldn't be too hard to take the same basic structure and modify it to be a different fantasy series. They nearly all have the same basic elements:
1. Somewhat naive main character who discovers hidden talents along the way (usually magical).
2. The 'enemy' who was defeated long ago and is now returned.
3. A quest, usually involving a long journey into the heart of the evil realm.
4. A war, usually occurring alongside the quest
5. Some very long lived person with strange powers who is the backbone of the 'good' side but doesn't actually get too involved (Gandalf wannabes)
6. A smart-alec rogue type
7. A magical animal or two
8. "Elves" and "Dwarves". Wven if they are not called by those names, there's always a couple of races or peoples that are basically the same.
I could go on. Note also that some of these similarities, such as 1 and 6, are common across many fantasy novels but are not necessarily based on Tolkein.
As for the Salvatore fanboys, I should point out that "The Dark Elf" trilogy is one of my favorite series. Drizzt and Menzoberanzan (sp? - I can never get it right) seem very original to me, maybe based a little on Elric of Melnoborne (sp? - long time since I read it) but certainly not LOTR.
The hardest part about creating a mod based in a non-D&D world would be implementing the rule changes needed to restrict characters and abilties, or to create new races and abilties. I'm not even sure it's possible to create totally new races and abilities with the Toolkit, unless they are just simple modifications of an existing D&D race. In particular, the D&D magic system is very different from that of most fantasy genres. I suppose you could just have the fantasy world with the D&D rules, but I think that you would risk losing some of the atmosphere unless you are very restrictive with the spells and abilities players can use.