How come that Yukiteru won if Ninth was still alive?
When Deus saved Ninth, maybe he kind of disqualified her from the game, so she's not a player anymore and doesn't have to die.
  I don't remember if this was mentioned or implied. Was it?


Actually, the rules aren't "The last survivor wins" but "The last diary owner wins". When Ninth came back, she had no diary anymore, because she already destroyed it to kill herself in the save. So after Yuno's death, Yukiteru was the last diary owner.

Besides that, Murmur doesn't seem to care about the winning conditions as she nearly made Yuno the new god even though Yukiteru was still alive.