It's full of groups that were doing overdubs before Queen, but I probably misunderstood here, since it's a cliché that anyone knows, even the most ignorant person about rock music. What exactly did you mean?
As for originality, there wasn't any; they simply played 40 different genres instead of two, at most three, like other bands did. This could still be a positive thing, I'm not arguing about that (although I don't think it is), but every single genre they tried already existed, and often it was done better (listen to Zappa, T. Rex, Slade, just to name a few). The exception is "Stone Cold Crazy," which is indeed an avant-garde thrash, although, as I said before, the Yardbirds had already arrived at that with "Stroll On," even if I admit that Queen went much further. They made memorable tracks, with strengths in their arrangement (but beware! Sometimes their excessive baroque style in arrangement was a weakness!), a striking melodic talent, and the amazing voice of the vocalist. However, I've heard very few completely good albums, and none were masterpieces. The fact that no one sounds like them doesn't mean they are too genius for anyone to imitate; it's due to what I said earlier: Queen don't play a single genre, but 40 genres, and yes, no other band besides them tries to recreate these 40 genres! However, there have been musicians who, from time to time, have done something that reminded one of the genres interpreted by Queen (look at how much that idiot Mika has sold recently!).
They're a good band, too underrated by critics, but frankly, I don't see their importance; if they had never existed, it would have been the same thing (precisely because no one follows in their footsteps, we can say that their influence has been nonexistent, despite their great commercial success).
Feel free to listen to them, by all means! But let's not say things like "they're unclassifiable," because that's not true, and especially let’s not say "they're great because they're unclassifiable."
