I wouldn't mind Juventus or Atletico.
Good, strong teams who are always "close" to winning it.
Monaco had a lot of luck and easy draw till now (Leverkusen, Tottenham, Cska Moscow, Man City, Borussia) and they are inexperienced.
Real is the strongest on paper, but best teams on paper don't win every time.
I wouldn't want to see Juve-Atletico in semis, because I think that both of them can harm Real.