SideM: 99% idol x idol shipping, I think I've seen only two images of SMP being into the idols.
CG: 15% (too any to list, some characters lile Atsumi exist to sexpest girls, the ChiChis being gay, Kanade, etc)
ML: 15% (too many theater role-based pairings, Yuriko is either riding Anna or being rode on by monsters, etc)
AS: 11% (Makoto being "the boy")
SC: 10% (mostly SHHis and Luca and old Oosakicest jokes)
GK: 10% (Lilja/Sumika, Sena stalking, Rinha being a lesbo)
Source: Pixiv-induced nightmares.