Up until 2009, Barcelona were not even in the top three. 4 years of the most dominant team on the planet and 1 player doesn't suddenly elevate them to be above United and Bayern. If anything, they're the Liverpool of the 70's and 80's and will probably struggle to replicate their success once mighty mouse fizzles out.
Seriously, name me a great Barcelona side was that revered other than Pep's? The early 90's side was decent, but they got absolutely spanked by an AC Milan side that was and probably still is the best side of all time.
United otherwise have had 5 great teams historically:
The Babes
65-70
91-95
96-2001
06-2011
Barca has a fantastic side in the late 50’s/early 60’s. They were the first team to eliminate Real Madrid from the European Cup and they had won many domestic titles, competing directly against Di Stefano’s Madrid. Their stars were Luis Suarez (won Ballon d’Or in his time there), Kubala, Kocsis, Czibor. Should’ve won the European Cup, but got really unlucky against Benfica in the final.
In the 70’s they’ve managed to sign the best player in the world, Johan Cruyff, alongside his compatriot Neeskens. Cruyff had won 2 Ballon d’Ors there.
80’s were less successful, but they still attracted top talent like Maradona and Schuster.
Cruyff’s Dream Team, even though they could field 3 out of Romario, Laudrup, Koeman and Stoichkov at the same time, was definitely a historic side (and yet another Ballon d’Or, by the way). Won the European Cup in 1992 and, although they’ve lost in 1994 (it was far from an all-time AC Milan great side at the time by the way), they still showed their quality that year.
Then you have good sides of the 90’s with Rivaldo, Figo & Dutch contingent. Then 2004-6 side with Ronaldinho. Only then there’s Pep’s tiki taka & Enrique’s MSN side.
It’s hypocritical to criticize their European record pre-Pep while also bigging up United that underperformed in Europe for a club of our stature.
The Babes weren’t better (at least significantly) than Barca of the 50’s. They probably would’ve, but who knows. Their Dream Team was better than our early 90’s vintage, even though Robbo & Hughes won us the CWC final against them. Etc.