But, that is a purely subjective opinion. A band only has breadth and depth if you subjectively like a lot of their songs and like a lot of their songs over a long period of time or in a number of different genres. I think a musician can be an objectively good musician, but I don't think you can really have an objective opinion on whether songs are good or bad. I mean, a great musician might make nothing but bad songs from a subjective point of view.
For me, the Beatles don't qualify in either of those things. I think a few Beatles songs are okay, but if I never heard another one, it wouldn't bother me. So, to me, they have no depth or breadth. They are just a pop band that had a few good musicians in it and sold a lot of records. Personally, in that genre, I much prefer the Rolling Stones, and I'm not a big fan of them. For my taste, they have more breadth and depth than The Beatles.
Still, I think the Beatles are a "great band", that just isn't within my taste. But given that everyone's taste is different, I don't see how any definitive position can be taken on which band is the "greatest."