That's always been interesting to me, as well as the fact that the most poisonous relationships possible tend to be very popular ie Cloud/Sephiroth
The 'female gender norms ' part was always rather strange to me, because there are plenty of fics based on things like coughing up flowers, your soulmate's name being tattooed into your skin at birth, or that wolf pack dynamic thing. That's possible, but not subverting gender norms?
Re more female characters in canon, the dynamic doesn't change much even in female rich canon.
Danganronpa always has an even gender split, because the premise is a class of 16 students have to murder each other.
This is the AO3 page. The lead character always has a girl and a boy as their major assistants. The dynamics are too complicated to explain here, but the top two relationships are M/M, followed in distant third by a canon ish M/F(the relationship is a bit ambiguous, but is a very close bond (Disclaimer: I ship it)
Resident Evil has a very good gender split, with very little romance in the main game.
Here is the AO3. The first two are M/M, followed by Leon/Ada, which I think is the only canon relationship.
There are lots of relationships and a lot of female characters of varying types in all the Final Fantasies, but by far the most popular is XV, which has the most opportunities for M/M, despite being the youngest. The only F/M relationship on the list is Noct/Luna, which is saying a lot considering Nyx is on the list.
Kylux even manages to trump the massive following of Reylo in the Star Wars ST.
Edit: I looked into
Attack on Titan. Second most popular pairing is Marco and Jean, a very minor character and a fairly minor character, so I don't know if the amount of focus given in canon is so important.
Aside: 4% Male? I'm a monster!