All of these should be fairly competitive:
Manchester City v Barcelona (Would not be shocked if City took this one)
Olympiakos v Manchester United (Toss-Up)
AC Milan v Atletico Madrid (The only sure bet, Atletico)
Bayer Leverkusen v Paris St-Germain (PSG)
Galatasaray v Chelsea (Slight leaning to Chelsea)
Schalke v Real Madrid (Real Madrid)
Zenit St Petersburg v Borussia Dortmund (Dortmund)
Arsenal v Bayern Munich (Bayern, but it won’t be a cakewalk)