wingsandsword
Legend
I think LotR was only a minor influence to Gygax himself. . .Gygax seemed as much or more influenced by Robert E. Howard, Jack Vance, Fritz Lieber and Poul Anderson, and Michael Moorcock than by J.R.R. Tolkien.meh. D&D is medieval based because the game started out heavily influenced by LOTR (in spite of what EGG said)… the basic appeal of the game was 'hey, you can play an elf and fight orcs in this vaguely medieval world'... the nice thing about D&D is that it's bendable enough that if you don't want to use a medieval setting, you can make up something you do like...
. . .but Tolkien was more popular and influential than the rest of those authors and later authors and players drew more heavily from Tolkien than others in their own campaigns and works, meaning that it's influence on D&D grew rather quickly.
Hence before long D&D became largely a Tolkien pastiche typically set in a fantasy version of western Europe with elements of the other authors and inspirations grafted on, like Vance's magic, Moorcock's concept of law and chaos, Anderson's paladins, Lieber's thieves, Howard's barbarians, Monks from Kung Fu movies, Clerics from the Crusades etc.