No other pop girl is doing Blackout. Those beats and production was made for Britney's sultry and kittenish vocals. Plus how it perfectly fit the situation around her life.
Also no one else can d
Back to basics. The faves (that could sing) can do the songs, just not as good as Xtina, you need power, clarity and agility to do that "heeeyyyyy" note in Ain't No Other Man.
Literally all of them, no one else has the vocal range, dynamics and song writing ability to match.