Over at Slate.com, Danielle Maurer gives four reasons why she believes J.R.R. Tolkien was a genius. Here are the first two:
World-building ability: As far as I’m concerned, no one has ever topped Tolkien here. His world has such depth and feel to it. There’s always more to explore and more to find out about the people and the places and the things and … you get the idea. I can and have lost myself for hours in Middle-earth (and Valinor). It takes such a mind-boggling amount of effort to do what he did—and do it well—that I can’t help but call the man a genius for it. Relatedly, you have:
Languages: You can speak Tolkien’s languages. It takes a huge amount of talent and ability to create a language, and Tolkien did it more than once. They are beautiful, and many of my favorite moments in Lord of the Rings are the ones that feature Tolkien’s insane linguistic talent. If you haven’t heard it, for the love of whatever you consider holy, please listen to the man speaking Quenya:
After giving two more reasons for why she believes Tolkien was a genius, Danielle concludes:
Put all that together, and you get a rare man.
The question details ask for plots that “blew my mind.” I honestly don’t think I could give you specific examples of Tolkien’s “genius” because there would simply be too many.
And it’s hard to beat the amount of sheer influence Tolkien has on modern writers. I mean, play a game and reread Harry Potter, keeping track of the scenes/ideas that are lifted from Tolkien. There’s a lot of them. He made elves into majestic beings in a way that no one else had really ever done—but which is now standard in the fantasy genre. I will readily acknowledge that I owe at least half (and probably more) of my own fantasy novel to Tolkien, and I can only hope that my books will enjoy a twentieth of the popularity his do.
I don’t feel like this answer is adequate enough to express how much of a genius I believe Tolkien is, but hopefully it at least gives you an idea of why I admire Tolkien so much.