The Band were so great because every single member had an equally important role.

Richard Manual, certainly, was the best singer of the bunch, both technically and in terms of emotional expression ~ but only by a pretty small margin, of course, since Rick and Levon were also so excellent. Rick and Levon probably displayed more "individuality" than Richard, each with a very recognizable vocal persona.

Richard's incredible range dictated that he took the high harmony "background" part in a lot of songs, or more precisely, in parts of a lot of songs. The band split up vocal duties among the three main singers more than any other group, routinely assigning different parts of a single song to different members. For example, check out "King Harvest," where Richard sings solo most of the time, and Rick and Levon harmonize on certain key lines in each verse.

But it's no accident that the few Band songs with an absolutely solo vocal generally featured Richard Manuel.

Robbie was not only the main songwriter (and thus, in a sense, the "brains of the outfit"), but also one of the finest electric guitar players ever ~ a "mathematical guitar genius," in the words of one Mr. Bob Dylan.

And then there's Garth, who never sang a note (far as I know) but made an incredible contribution as a multi-instrumentalist.