Phil Collins/Genesis: Stop it. I know it's lightweight and the consensus is he wasn't as good as Peter Gabriel.
Phil Collins performed the Gabriel era Genesis tracks live without missing a figurative beat in concert.
IMHO, the loss of guitarist Steve Hackett was a much bigger blow to Genesis than the loss of Gabriel.
As for the original topic, there's no way I can narrow it down to five, much less twenty, so I'll bow out of this thread gracefully. But you can rest assured that Rush, is in my top 5, even though I may be in the minority here.