If he was alive and not Hokage (as in, if Tsunade never went into coma etc.), he'd probably still sit there hidden, waiting for the opportunity to take over like he did during Pain's invasion.
If he somehow became Hokage and the Alliance's leader (I dunno, if his manipulation of Mifune wasn't discovered or if Mifune appointed him without manipulation), he'd obviously go against Obito. But some things during the war would have obviously gone differently. He would have probably tried to keep Naruto confined at all costs (unlike Tsunade who believed in him). The Kage would have probably died to Madara. I don't know though, there are many options.
I wonder, would he be affected by Naruto's Ninshuu if it came to it?