It has been said that virtually every fantasy novel written since can be compared to the Lord of the Rings. It is probably because Tolkien did such a good job at bringing the storytelling elements of "ye olde" myths into his story, and weaved it into a whole new world, rich in history. It seems hard to tell the difference nowadays between people ripping off Tolkien, and making use of story elements that have been in use since the dawn of time.
How many people actually realise that Elves, Dwarves and Trolls are taken directly from Scandanavian (Viking) myth, and aren't an invention of the D&D craze?
I actually don't see a huge similarity between Brooks and Tolkien, other than the usual plot elements of a young innocent drawn into a quest by a wise old wizard, accompanied by a group of more experienced warriors (including elves, men and dwarves), to defeat an ancient evil "big bad" being about to conquer the world with his evil magic, with lots of big battle scenes outside a underdefended human city, which gets rescued at the last minute.
Ok, perhaps I see your point.
But I find more interesting the differences in the stories. I really like the idea that dwarves, trolls, gnomes having been branched of from humans due to the aftermath of the "Great Wars", rather than being ancient separate races, was an interesting take on things.
And the great magical power of the Sword of Shannara simply being the ability to reveal "truth" was an eye opener, and different to anything I had seen before at the time.