I completely agree with Lloydc. They were not even close to being the best band ever. (I could easily name a hundred or so better bands.) I will readily admit that they were very successful, but then again, so was ABBA, Styx and other pop bands of that same time period.
IMHO, they were a decent, but not great, band, especially after the girls joined the group. (Before that they were not nearly as successful, but a much better band.)
Anyway, my two cents worth.