In nearly every stanbase here on ATRL, at least 75-95% agrees that a few album tracks from your faves could've been huge smashes (or at least moderate hits). The question is, what are the songs that your fave(s) never released that could've been huge? Also, keep ongoing eras out of this (MDNA, PF:RR, Stronger, ect.), and keep it to completed eras.
For me:
P!nk:
Split Personality - Why this was never released after "You Make me Sick" still bothers me to death. This screams smash.
Humble Neighborhoods + Catch Me While I'm Sleeping - I know anything from TT would've flopped no matter what, but I still wish these two got a proper release (along with a proper LTK video)
Cuz I Can - I'm surprised this only got a very limited release in Australia. I think this could've been a 4th hit from the album in the US (why they stopped at "U+Ur Hand", I'll never understand)
Heartbreak Down - She could've had another top 5 hit with this one, after RYG and FP.
Gaga:
Boys Boys Boys - Come on, it's obvious this would've been big, especially after "Paparazzi".
Dance In The Dark/Monster - Either one would've been hits tbh. "Dance In The Dark" had an opportunity to have a epic music video, and "Monster" would've been huge.
Scheiße - After MTN, she could've waited, launched this at the Grammys, and slowly worked the BTW era back up.