^^ What lack of chart-topping?
The only chart she lacks topping really is Hot 100 (and the Airplay cause she only receives pop support)... most of others charts (internationally) she has done it more than 3....
You were just wrong to start comparing Gaga's 2 #1s (and possibly 3) to Britney whole career, while Britney career >>>>>>>>> Gaga's 3 Hot 100 #1s.....
Who cares about topping Hot 100 when you are able to be the best selling female musician of the decade?