Statistically, they would be the best in the CL era, 3 in a row and 4/5 years. The 3 in a row equals Ajax and Bayern record from the old European Cup days, but they would still be behind the Real side of the late 50's and early 60's who won 5 in a row and 6/10 years.
But they've only 2 league titles in 9 years, aka the Cristiano era, and they were 5 years apart. While Barca haven't done b2b CL win they do have 2 trebles to their names and have also won their own domestic league b2b also.
I still take Saachi/Capello Milan and Pep's 1st year Barca (it was by far the best balanced team) over them in a match. Both those teams would match up physically with this current Real team.
Like I mentioned earlier, stats wise would call them the best, but they aren't really a memorable team when I think about to all the club teams I've seen in all the years of watching.
Cristiano makes the difference in that team, if you took him out they would automatically lose half of his goals (given the replacement would at least hit half of Cristiano output as a bare minimum) and

relying on Benzema.