I have also done some research on Japanese mythology and how it relates to Naruto and I don't think that Sasuke represents Ninigi-no-mikoto to be honest. However, I think it's good that you spent time doing some research on Japanese mythology.
I think though, you should look at the deity Susanoo, as I'm pretty sure Sasuke is more related to him than he is to Ninigi. I've also read theories that connect the gods Raijin & Fuujin to Sasuke & Naruto, these two Japanese mythological deities (Susanoo & Raijin) have much more similarities to Sasuke, than Ninigi-no-mikoto does imo.
Ninigi-no-mikoto I believe represents the sage of six paths, To me it seems that the story of the Elder son & Younger Son. (Uchiha & Senju) are an adapted version of the story of Konohanasakuya-Hime & her Elder sister Iwanaga-Hime.
ex: Ninigi chooses to marry Konohanasakuya (Youngest Daughter) over Iwanaga (Elder Daughter) Iwanaga thus curses the descendants of Konohanasakuya, and humans (descendants of Ninigi & Konohanasakuya) are said to be short and fleeting, like the sakura blossoms, instead of enduring and long lasting, like stones.
ex: Sage of the six paths chooses the Youngest Son (Senju) as his sucessor over the Elder Son (Uchiha), thus the Uchiha pass down the curse of hatred against the Senju throughout the next generations.
I realize its not 100% similar, (the senju do not have short lifes), but there are some similarities, (elder sibling feels betrayed and a curse involving the younger sibling is formed). Also this idea is not mine, I read it a while ago on a naruto blog, but it made me a believer lol.