Sacchi coached Milan 4 years the first time. As long as Guardiola has coached Barcelona at the end of this season. Both have won 2 European Cups, but Guardiola has 3 league titles to Sacchi's one. What makes you think Milan were the better side?
Liverpool couldn't compete in Europe obviously, but it's not like we won the league every year either.
Dont get me wrong. Barca may turn out to be the best club team ever but for me they still have to prove they have earned that accolade. Theres too many fans who have given that to them already - and yes its predominantly the Sky generation.
You can't directly compare which teams are better just by saying one team has won two cups and the other three - it is at the end of the day a knockout competition. Also, the current competition is easier to win, in my opinion, than the older one in which you first had to qualify by winning the domestic league then maintain your form over the next year for the European stages. Barcelona winning a domestic competition in Spain is like Porto winning in Portugal or Rangers in Scotland - I think its harder to compare that with winning the Italian league.
The truth of it is though that unless there is a direct European Super League you couldnt compare the teams properly anyway - and that would obviously be impossible over different timespans. So all you are left with, really, is your opinion.
In my opinion, as I said, Barca play pretty football but they lack power. That's why they got outmuscled by a ten-man aged Chelsea. In my view, those sides i mentioned had both prettiness and power which is why they could produce beautiful football.
Now maybe Barca have a system with their academy etc. whereby they can produce more consistent results over the next ten years which will allow them to win more trophies however, in my view, Sacchi's Milan would come out on top against this Barca side even though Sacchi didnt manage to build the dynasty that Barca have under different managers.
But for a team campaigning over a season, Barca haven't proved to me that they can be regarded as the best ever (yet).
Just my opinion.