The obvious: “Bohemian Rhapsody”. It’s simply one of the most unique pieces of music ever created. Overplayed or not, it’s one of those songs which will never fade away because it’s so original.
As much as I want to pick something less obvious, this is the answer. It may suffer from overexposure but it is their best and most original work.
Call it predictable, but my answer is Bohemian Rhapsody. An amazing piece of music that has held up extremely well.
We Are the Champions is about the only one I get any enjoyment from. 40 years ago I would have also included its B side. I have the 45.