They were very good, though I probably wouldn't call them great. They seemed to slip in out and out tedium quite often. I probably can't blame Jackson for that, though, as Tolkien wasn't really all that great of a writer, his world-building skills aside. His pacing left a lot to be desired and he wasn't exactly a master at dialogue. Still, the novels are massively important to modern fantasy and even gaming. They've since been surpassed many times, on many different levels, by better writers, but that does not diminish their impact on the genre.
Still, I do hold Jackson responsible for the Frodo x Samwise romance saga. It got a little crazy at times and I hated the film version of Sam.