Also, MSN has 106 goals between them in all comps.
So let's look at the contenders:
Bayern 2012-13 -- They lost once in the Bundesliga. In the second half of the season, they never lost and only drew once. They finished with 91 pts, a Bundesliga record (remember the BL is only 18 teams, so they play 2 less league games than many other European teams). Goal Difference was +80. They allowed 18 goals. They won the league by 25pts and clinched on April 6. Maybe the league wasn't great, but they did have Dortmund who was coming off back to back league titles and would be their opponent in the CL final. They beat Barcelona 7-0 on aggregate in the CL semi. They also won the DFL Supercup and the DFB Pokal. Beckenbauer and Rummenigge called this team the best Bayern team ever. High praise. And of course, they ran the coach off for Pep. NOTE that if Pep wins the CL league this year, you could conceivably make a case that his BL dominance extends this to a multi year run like Barca, below.
Barcelona 2008-11 -- They won 6 trophies in the 2009 calendar year. First Spanish Club to the league, cup, CL triple in the 08-09 season. In the 2009-10 La Liga season, they won the league with a European record 99 pts but got Jose'd in the CL semis by Inter. In 10-11 season, the team won the league, Cup, CL triple again.
Manchester United 1998-99 -- "Football, bloody hell." Really aren't a contender for "best" team. They hardly dominated any competition, but memorably won the treble with some absurd moments (Giggs in FA Cup semi extra-time against Arsenal. Ole in stoppage time in the CL final)
Those are likely your Champions League era candidates. The Galacticos never delivered consistently in Europe.
Go back to the European Cup days and you're talking about Milan in the late 80s, Liverpool in the early 80s, Bayern in the late 70s, Ajax in the early 70s, and Real and Benfica in the 60s. The problem with those 60s and 70s European teams is that we don't really know that they were better than Santos (for instance) at the time.