I believe that Hashi and Madara were the brothers reincarnation. The sage cared about the tailed beasts. I think he might only appear to the reincarnations that the tail beasts acknowledge. I think only the person who will cooperate with the tailed beasts gets to talk to the sage.
While Hashi did have natural talent and a strong body, he also had an overwhelming desire for peace and was willing to give up his life just to get the Uchiha Clan to talk about peace with the Senju Clan. If that doesn't show Ashura's ideals, I don't know what else would. He also thought the tailed beasts were powerful tools to keep the clans in line so I don't think the sage would have bothered meeting him.
I think the sage is meeting Naruto now because he has come the closest to Ashura's ideals than any of his predecessors, if he doesn't get Naruto to grab this chance now there will not be peace for a very long time, if at all.