This idea will probably either be considered brilliant or stupid! Anyway...
It has occurred to me that parallels to the "Besser era" can be found outside the Stooges, if one defines "Besser era" something like this: A team/group/show/etc. loses an irreplaceable performer, at a time when they're already well past their artistic peak; and the empty spot is briefly (<-- key word!) filled by a basically talented person who does what they can, but cannot succeed because (1) they don't quite fit in, and (2) nobody really could have filled the lost persons's shoes anyway.
A couple of examples I know of:
GENESIS (the band) - Phil Collins was kind of their "Shemp" (a member of the family, so to speak, who took over for the "Curly" of Peter Gabriel), and when he left, Ray Wilson was brought in as the new singer. Through fault mostly other than Ray's, this didn't go well and Ray was quickly shoved out.
CHICAGO (also the band) - Original guitarist Terry Kath accidentally killed himself in 1978, just as the band had severed ties with their longtime management. He was replaced by the very un-Terry-ish Donnie Dacus. The band managed to maintain their success somewhat through the next album, but the next one bombed, and Donnie was out.
Anyone know any other examples? Or is this just a really stupid question?