As i said,it's open for interpretation.No doubt that Barca are quality but they are not the greatest club team of all time.I'll agree within the two year period but Real Madrid have won the CL five times in a row & the first ever winners..Even if that was back in the 50's,i don't see Barca replicating that feat.Also they won the La Liga four times in a row in the 50's.
La Liga - 1953–54, 1954–55, 1956–57, 1957–58
CL - 1955–56, 1956–57, 1957–58, 1958–59, 1959–60
So based on trophies & as you pointed out historically,Barca are not the greatest club team ever.Simply put,it's Real Madrid.