Album wise, I wouldn't say BOMT is iconic at all. The single was phenomenal, but the average person is going to have a hard time remembering what the other singles were or what the album cover was.
It's too recent to know for sure, but I have a feeling people will remember more from TF as an era. Especially if you include TFM.
Both were iconic in their respective eras and started a revolution. If anything I say GaGa has had much Britney-like success these past years its undeniable she's taking that same path to Legendaryness