I was watching a bit of the Robert Plant of Glastonbury, and had he not been 'Robert Plant formerly of Led Zep' and played some Led Zep songs there's absolutely no way he would have had a prime main stage slot on his solo material alone. He'd be playing early doors on the world music stage at best.
On the other hand, Jack White most definitely would have (and kind of did anyway) make it as a solo artist even if he hadn't have been in the White Stripes.
This thread isn't about whether an artist's music is better solo or in a band, it's about whether the solo work would have stood up in its own right without the 'legacy' of being in a popular band first.
Other artists who would have made it as a solo artist without their former band: Phil Collins.
Other artists who would not have made it as a solo artist without their former band: Ian Brown, Morrissey (maybe?).