Lanefan said:
AD&D *is* D&D. So is 3e. So is OD&D. So yes, the game *can* support all sorts of settings...just pick the right edition, and go.
Yes, but these settings were written with D&D in mind.
It's like saying that D&D is flexible because it can emulate D&D.
Sure, if you drop the fluff and just go with the combat system, you can invent just about any setting to go with the crunch (as long as you assume vancian magic, wealth/level and so on...)...but it doesn't make the game flexible, since, as noted earlier, this can be done with virtually any game out there.
LotR can easily be emulated by taking something like OD&D or 1e and really slashing back the magic; I've seen it done, to good result.
Again, D&D doesn't work without healing magic and magic items, at least at mid-high levels.
If you tried to play LotR with D&D, the party would probably need 5/6 days of rest just to regain the lost HP after just about any fight.
Can you take a D&D party, strip it of magic items and call them "The Fellowship of the Ring"? Sure. Would it make for a fun game? Depends on the players and the DM.
Would it be balanced from a rules standpoint? Probably not.
Wheel of Time can be approximated closely by replacing all spells with psyonic abilities, then changing what those abilities(spells) actually are to suit the canon. I considered trying this once but never got around to it, and it'd help if the series would ever finish (not so likely now).
Actually, there's an official d20 WoT game.
It's not bad, check it out if you like the genre

Anyway, it uses scaling bonuses to AC to make up for the lack of magic items, and the magic system's been completely redone.
If D&D could emulate it so well, why all the changes? Why didn't they just make it a setting for D&D ( since, IIRC, WotC was the publisher for both)?
Song of Fire and Ice can probably be done via some tweaking of the Birthright setting; it somehow seems to fit, and though I'll not be the one to try it I'd be interested in hearing the results if someone did.
I'm not familiar with Birthright ( I know the setting but I never had a look at the rules system ), but Guardians of Order put out an "A Game of Thrones" RPG some years ago.
Again, the system needed a substantial overhaul to work and make it true to the books.
This doesn't make D&D any more flexible, IMO, it just means that the d20 system ( like just about any other rules system out there ) can be used to describe a guy that waves a sword (in D&D, though, that guy never learns how to dodge a sword blow

).
But if half the PHB (namely races, spells and classes ) has to be replaced to make a setting work, I'd say that D&D doesn't handle that setting well at all.
The rest, I'm sorry to say, I'm not familiar with...though from what I gather the 1e game I've been playing in on and off for many years has a rather strong foundation in Moorcock; I just keep missing the references.
If you're asking specifically what 3.x can do out of the box, then of course it's limited. If you're asking what the game as a whole can do in the hands of a competent DM, I think you'd be mighty surprised.
Lanefan
Yeah, a DM that's good enough can make the system work in most circumstances ( he'd probably do better with another game system, though, and still he'd have to make some substantial changes ).
This doesn't mean the game system is flexible, though, just that your DM's mind is
