The greatest fantasy/sci-fi series of all time are, in my humble opinion:
Lord of the Rings
Red Rising
Stormlight Archive
Hyperion Cantos
Wheel of Time
Chronicles of Narnia
CS Lewis’ Space Trilogy
...
Loved Iain M Banks ‘Culture’ works. Proper space opera. I suspect my reading of them today would be far more dystopian, but looking back his lead characters were always on the fringes and uncomfortable with the role of humanity in a galaxy run by AI (the ship Minds). I was gutted when he died, it was the first time I felt a personal sadness there would be no more books