Manchester United, Real Madrid, Barcelona, Ami, Chelsea and Beijing Guoan, which of these teams is stronger?

This comparison, first take out Barcelona, because Barcelona is known as the cosmic team, so it is not suitable for comparison with the team on earth, and it is the strongest. Then the teams on earth will be taken to Beijing Guoan, and the other four are European giants. Beijing Guoan is the weakest, and the strength of these four giants is relatively close, but Chelsea is a reconstruction team, which is very unstable and slightly weak. Then ac Milan has just embarked on the road of revival, which should be behind Manchester United and Real Madrid, and Manchester United should have a facelift. Barcelona, Real Madrid, Manchester United, ac Milan, Chelsea, Beijing Guoan.