It really depends what you regard as success. Marr has followed his muse and made the music he has wanted to make, whatever that is, until relatively recently in a band environment either as a member or as a guest (Electronic, The The, Modest Mouse, The Cribs, etc.). And he's been able to make a good living out of it. That's success by any standard.
Morrissey's been able to do mostly the same, though his commercial viability is shot to pieces : he can't get a record deal, is playing smaller venues than he has done in 20 years, and is uninsurable from a tour perspective. That's not really success in my opinion.
Heck, you could call some of his shows 'record breaking' for having the largest number of unsold tickets for the venue without cancelling, if you want to put it that way.