Manchester now have a huge advantage that they can play at home, with the 1-1 score in the bag. That's no guarantee they'll go through, but they're in a good starting position and I think they're heavy favorites too. Atletico are not a strong team on paper, but they have not convinced this season. United not always, but individually United are still far above Madrid. And Ronaldo knows better than anyone how to score goals against Atletico Madrid.
Actually, Manchester United will be more enthusiastic when playing at home with a 1-1 capital in their pockets because I believe that Manchester United will improve their performance in order to win at home and ensure that they qualify for the next round.
It's not all about a Ronaldo, but about how to play really well in order to win against Atletico Madrid.