Probably Britney. Anyone who knows Gaga knows Britney but Britney is really the bigger celebrity. The Little Monsters really overrate Gaga's relevance.
I don't understand why some illiterate people are bringing up chart receipts when the OP is asking who's the biggest celebrity not who's more successful nowadays?
? Britney's last celebrity peak was in 2008 with Womaniser? Gaga has been bigger since which makes her the bigger celebrity and bigger household name.
The thread is about who is the bigger celebrity/household name 
