A Class: Real Madrid, Barcelona, Bayern Munich, Chelsea and Manchester United (Although they are temporarily out :p) I'd say.
After that teams like: Atletico Madrid, Manchester City, Arsenal, Liverpool, Dortmund, Juventus, PSG etc.
Atletico and City are very close to being A class, but I don't expect Atletico to do as well this season and City are just underwhelming in the Champions League.