I’ll stick with movies:
Though “Alien” is an excellent sci-fi movie, the sequel, “Aliens” ups the ante and is more exciting.
“Terminator” was a fun time travel paradox but the sequel, “Terminator 2: Judgment Day” was more polished with a more complex story and CGI instead of stop motion special effects that are still stunning to see. (Like “Aliens”, both movies were under the helm of James Cameron)
“Star Trek: The Wrath of Kahn” was heads and tales better than “Star Trek: The Motion Picture”.
“The Empire Strikes Back”, the 2nd of the 9 plus Star Wars movies is still considered the best by fans.
“Cruella”. It is actually a prequel to “101 Dalmations”. It is so well written and acted, it makes the classic children’s story it was inspired from seem almost trite.