Is Warhammer 40k one of the greatest crafted fictional settings ever made? What else compares to it?

Where do you believe Warhammer 40k ranks amongst the greatest fictional settings ever made. The sheer quantity and overall quality of the lore and world building is simply incredible. The scale and grandness of the setting is so fascinating. I guess the closest universes I can think of are Tolkien’s Middle Earth, Frank Herbert’s Dune and George RR Martin’s A Song of Ice and Fire. But still I truly believe Warhammer 40k is just as well made as those settings. The world and atmosphere feels so large and real. The history and timeline is long and complex. I get that sometimes the books are more pulpy fiction rather than quality literature and that’s what probably holds the setting back quite a bit, but for me the overall universe makes up for it. Where does Warhammer 40k place amongst other fictional settings for you?