As for Nagoshi himself, I am really unsure if he is deserving of his Miyamoto status at Sega. Like, maybe it is kind of sad that others got left behind because of their failures...but Nagoshi still doesn't compare to Yu Suzuki or Yuji Naka, and other more unknows like Ohba, Kodama, Oguchi, Nakagawa and Uchida etc.
When he got his team in 2000 with Amusement Vision, it was actually the smallest among the 9 dev heads, implying that he still had the most to show for at Sega.
In my mind, he is more equal to Masayoshi Kikuchi who directed Jet Set Radio around the same time Nagoshi directed Monkey Ball. Now, Kikuchi just manages the mobile division.