40k, gundam, the expanse, dune, starcraft

The thing about sci-fi is that it's at its best when it's engaging with questions about humanity's place in the universe as we expand beyond Earth, create technology that is in many ways beyond us, etc. It's like cyberpunk for Bloomers (except maybe 40k but even then it sort of is, just pessimistic within that frame). Problem is, the tropes of sci-fi don't inherently lend themselves to intelligent interaction with these questions, so it ends up taking exceptionally good works in the genre to really be worthy pieces of fiction.

Contrast with fantasy, generally at its best with stories about heroism, with thousands of years of tropes built to do exactly that. Even lazy fantasy winds up being half-decent.