You can play the numbers game all you very well please, but you have to look at the bigger picture. In terms of maintaining longevity for this band, Stevie comes out on top, no doubt.
She has the most successful and continual solo career out of anyone from the band, and keeps them in the spotlight. Since Say You Will, it has been Stevie that has kept this band alive, albeit from a solo position. A greatest hits package, multiple solo tours, two studio albums, live concert releases, photograph exhibitions, album rereleases, television appearances, the list goes on.
Her American Horror Story appearance and featured songs helped bring the band to a younger audience, not to mention her talk show performances.
Meanwhile, Stevie has continually been criticized for doing nothing for this band. Yes, the publicity helps her own image and legacy - but one would be remiss not to automatically include FM as part of it.
Had Lindsey and Mick run the show the past 10+ years, there would be a chain of mildly successful Fleetwood Mac-themed restaurants... but that's just my opinion.
EDIT:: in regards to chart positions, the two songs Fleetwood Mac are most remembered for are Rhiannon (not top 10) and Landslide, which wasn't even released as a single.