This is hard but I enjoyed Blackout more. It's also still playable to this day. I know RoL is older so it would be unfair but that's what I feel. Heaven on Earth is orgasmic.
Sales have nothing to do with this. Most people bought physical copies of cds back then and Blackout was barely promoted.
Ray of Light is critically acclaimed, has won multiple grammies and has appeared on many "best of" lists. It's a pop masterpiece not denying that. But at the same time, Blackout is arguably the definitive pop album of the late 00s and was ranked 7th best pop album of the last decade by Time Magazine. It also never fully reached its potential because it wasn't promoted or handled properly. To completely write it off and say that one song from Ray of Light is better than the entire album is just.....
Ray Of Light is one of my least favorite madonna albums but I would still say ROL just because the title track is one of the best songs ever created. The rest of the album I don't use though.