Honestly, I think
21 had the potential. "Rolling in the Deep" and "Someone Like You" were HUGE, and then "Set Fire to the Rain" became a huge smash, mainly riding off of the success of the other two because she couldn't do anything to promote it due to her vocal surgery. If she would've actually tried to promote it, it would've been even bigger (even though it did go #1). The same is true for "Rumour Has It" and "Turning Tables." If she would've actually promoted them (and if it weren't for "Turning Tables" only getting released in select countries), I think they could've been #1 hits for her as well.
And Into the Groove isn't on the original tracklist, only on the non-US 1985 re-release but it was even left out of all versions of its 2001 re-release. 
