Ranking first is the “Fist of the North Star” parodied in “Gintama.” In episode 183, the OP mimicked the Cyborg Original.
Coming in second is from “30-sai no Hoken Taiiku”, parodying the “Virgin Balls” instead of “Genki Balls” from Dragon Ball Z; third is the Kyoto Anime “Raki Suta”, borrowing elements from Public Road Race manga “Initial D”.
The rest of the raking goes as follows (Parody – Source):
4. Food Wars!: Shokugeki no Soma – Jojo’s Bizarre Adventure
5. Sgt. Frog – Neon Genesis Evangelion
6. Osomatsu-san – Attack on Titan
7: Gintama – Neon Genesis Evangelion
8. Hayate the Combat Butler – YuGiOh!
9. No Matter How I Look at It, It’s You Guys’ … – Death Note
10. Gintama – Dragon Ball Z
Gintama ranks the most often as the parody, while popular sources include “Fist of the North Star”, “Dragon Ball Z”, “Neon Genesis Evalgelion”.