I saw a list of 100 sf movies people should see before they die. Nearly 20 were super hero movies. I wish people would quit conflating super hero movies with SF movies. Just because he came from. Another planet doesn't Make Superman a sf movie.
You don't know of any examples of the genres converging?
I would say it's sci-fi. If it's not-what is is? Lasers and robots and space travel....!
Christ- STAR WARS is a superhero movie!
Flash Gordon kinda sci-fi.
Not all sci-fi is 2001.
(I certainly wouldn't put any on my top 100 list...)
I would agree with RC. Most famous superheroes would come under sci fi.
Aliens coming to earth, mutated genes, people being bitten by genetically or radioactively modified creatures, billionaires with highly advanced technology, an alien race with sufficiently advanced technology that we view them as gods (Thor et al)... They all come under the banner of sci fi. Certainly it isn't hard sci fi (which is generally set within existing laws of physics and how we understand the universe such as Asimov would write), but sci fi none the less.
Off hand the only big name superhero I can think of who wouldn't come under sci fi would be Dr Strange, which I'd put under fantasy, but I am sure there are others.