Steve Winwood was bigger than the Spencer Davis Group and perhaps more successful overall than Traffic.
Phil Collins was certainly more successful as a solo act than Genesis.
Kenny Rodgers did better as solo than he did with the First Edition (though the group was later billed as “Kenny Rodgers and the First Edition,” his name wasn’t originally part of the group name).
Janis Joplin was probably bigger after she left Big Brother and the Holding Company.
Boz Scaggs was more successful after he left the Steve Miller Band than the SMB was at the time he left them. Later, Steve Miller eclipsed him.
John Denver did better after he left the Chad Mitchell Trio.
Rod Stewart was much more successful as a solo artist than with the Jeff Beck Group or the Faces.
Not a recording artist, but Joe Pesci became much more famous after he left Joey Dee and the Starlighters.
Don’t really know if this qualifies, but Robbie Williams seems to be bigger than Take That, though I’m in the US and missed all the Take That hoopla. In fact, until recently, I didn’t even know what Robbie Williams sounded like.
Sammy Hagar / Montrose (somebody told me he was also in Van Halen, but that’s impossible, as VH ceased to exist in 1985)
Cyndi Lauper / Blue Angel
Joan Jett, Lita Ford / The Runaways
Dave Grohl attained more time in the spotlight as the leader of the Foo Fighters than as the drummer for Nirvana, where he was overshadowed by Cobain.
At the risk of getting flamed
Post-Beatles, Paul McCartney formed Wings then went solo. I remember a second-hand story where, in the '80s, someone overheard some young’un exclaim, “Paul McCartney was in a band before Wings?!”
You could say Bob Marley is more famous than the Wailers, although it’s something of a piffling distinction (the band was originally just The Wailers, then became Bob Marley and The Wailers after Peter Tosh and Bunny Wailer, nee Livingston, left; and still tour as The Wailers).
Come to think of it, Stephen Stills was part of Buffalo Springfield as well, and he’s probably better known than that band as well. And as I went to look up info on the band at the All Music Guide, they displayed the following bit of trivia: “All four members of Crosby, Stills, Nash & Young were previously in notable '60s rock bands: the Byrds (Crosby), the Hollies (Nash), and Buffalo Springfield (Stills and Young).”
Curtis Mayfield/The Impressions
And about the Gloria Esteban example in the OP, I think the first video they released was just billed as “Miami Sound Machine.” They didn’t become “Gloria Esteban and Miami Sound Machine” until two or three songs later. The Gloria Esteban billing changes have always reminded me of an old Mad Magazine bit about the rise and fall of a star.
That doesn’t count. The Mothers was always Franks baby, and from early on, the band members were officially his “employees”, enabling them to get unemployment benifits, among other reasons.
There were a lot of people who played in his bands over the years, who went on to bigger if not better things. Off the top of my head…Dale and Terri Bozzio went on to form Missing Persons, Steve Via was all over the place in the 80s, Ansley Dunbar got rich in Journey, Ike Willis has a pretty good solo career. There was Wild Man Fischer, Flo and Eddie (who were already famous), Jean Luc Ponty, and probably a bunch of people that I’m forgetting.
