1. I wouldn't consider Britney's Womanizer/Circus era a comeback because Blackout is platinum in US, sold 3M WW. Gimme More is Top 3, and Piece of Me is Top 20. She also won 3 VMA's that year.
2. Mariah Carey had one of (if not) the biggest comebacks off all time with TEOM
3. JLO did have a comeback this year with On the Floor. Love? and I'm Into You are moderate hits.
4. CHRIS BROWN had the biggest comeback of the year. After Graffiti flopped, everybody said he was done, but he came back with a Top 10 single and a #1 album and a sold out tour
I'd agree Chris had one of the best comebacks I've seen...ever. He was a media pariah for a long time and a lot of people thought he would never see success again. Little did they know
Britney, of course, is always going to be on these types of lists involving comebacks and rightfully so.