Heck, even if you ask somebody who doesn't know the franchise inside out, they would probably have to agree that they are up there in the pantheon of legendary creative works that changed the culture forever. There is just something about the magic of Middle-earth that makes millions of people want to escape there with regular rewatches, re-readings, and many other activities besides. There is always something new to discover in a text that is this rich.
Obviously, it also helps that all things Tolkien are served by a fandom that is pretty much as loyal and enthusiastic as they come. The entertainment industry has long been aware that they will be a reliable audience for any kind of spinoff they choose to put out (even though they may complain about the quality) and, of course, they are more than adept at creating their own LOTR-themed entertainment as well.
In truth, every single meme that is made in tribute to the characters and storylines that happen in The Lord of the Rings only adds to its formidable legacy, even when they happen to be quite dumb. The mark of a project that will stand the test of time is something that doesn't always take itself so seriously, as Tolkien memes and their creators do not.