Janet's. Hers is more thorough/comprehensive, and doesn't leave out anything that anyone would expect to hear. Madonna's is all over the place. It ignores/snubs a number of hits, while conspicuously featuring songs that either flopped or only did modestly well. It almost seems like Madonna picked the songs she personally favors, while leaving off what she thought her fans could do without. Number Ones doesn't disappoint at all. Celebration, however, you have to be a 'sport' with. I was a sport with The Immaculate Collection and GHV2, I didn't wanna have to do it a third time.

^ Ditto. Janet's hits collections not only covers just about everything, but is also tracked in chronological order. Madonna's tracklisting is skewed.

Janet's!