I'd say TFM. It produced 2 massive WW number 1 singles and Alejandro was a big hit and it pushed TF's sales to about 14 million. If TFM wasn't released I think it would have stalled at 6-7. Also TFM made Gaga blow up and put her in a whole new league. Teenage Dream was huge though and much bigger than Born This Way era. There both flawless era's in terms of music, image, tours and videos (with the exception of Alejandro ).
Avril | Nirvana | Taylor | J-Law
Vampire Weekend | Gwen | The Smiths | My Chemical Romance
Rihanna | All Time Low | The Pretty Reckless | Blink 182 | Lana | Jake Bugg
Are we talking about The Fame (Monster) or The Fame Monster (EP)?
Because if we're talking The Fame (Monster), they aren't even close, and if we're talking The Fame Monster (EP) what metric are we supposed to go by considering we don't have accurate album sales numbers and there were only 3 singles.