The best would-be-singles from Lady Gaga's discography that were never released as singles:
1) Monster
2) Dance in the Dark
3) Scheiße
4) So Happy I Could Die
5) Hair
6) Summerboy
7) Greatest (....c'mon Cher...
)
8) Boys Boys Boys
9) Reloaded
10) Heavy Metal Lover
(Keep in mind I ranked these songs based on how well I think they would perform as singles, and not necessarily based on which song is "better" or which song I prefer.)
I honestly think Gaga could have smashed with Monster, Dance in the Dark, and So Happy I Could Die. That EP was simply full of hits-to-be. If Gaga were a commercial sellout and had generic, fun, non-controversial videos, she could almost easily have 6 #1's off of The Fame Monster: Bad Romance, Telephone, Alejandro, Monster, Dance in the Dark , and So Happy I Could Die. #1 may be a stretch for all of them, but they were all definitely radio- and dancefloor-ready.
Scheiße and Hair would also do fairly well, in my opinion. Right now, it hurts that Gaga has gotten some backlash and has lost some of her digital power, but purely as songs Scheiße and Hair are very catchy and radio friendly.
Summerboy and Boys Boys Boys remain two of Gaga's best, catchiest songs that were never singles, but I am glad she never released them; artistically I think she was far beyond The Fame by the time her last single from that album (Paparazzi) came around.
Greatest and Reloaded, two unreleased songs, would absolutely smash if touched up and polished; they are both layered with beautiful, seemingly effortless pop hooks that in all honestly are lacking in much of Born This Way. (As an aside, I still don't know if putting Cher on Greatest will make it any better)
Heavy Metal Lover, while one of my favorite songs from Gaga, would not do as well commercially as the others mentioned, but based on its dripping-with-sex, wildly infectious chorus could do moderately well.
I guess my point in making a list like this is, aside from the mass amounts of boredom I am experiencing from Gaga withdrawal, that Gaga has had many songs, past and present, that are commercially viable, radio-friendly songs that have not been released for various reasons. I respect Gaga for not succumbing to the gold-chase of so many other artists in the industry and releasing songs based on her own artistic vision and her preferences. It takes a lot to not only argue with your label, but to move on from albums/EP's full of commercial, ready-to-smash hits that were never released simply to respect her own artistry and move on to themes and music that better fit her ever-changing vision. So many other artists release as many singles as can make the label and them more money (and of course do remixes/other versions to increase sales); Gaga, love her or hate her, really stays true to herself and her creativity.
And it is so underrated 
I don't post very often, but I like to make my posts count. Today I just feel like with no Gaga news recently, we should sort of build positive energy even if Gaga's recent singles has somewhat underperformed. This fan base is way too negative to be spearheaded by a love-yourself-no-matter-who-you-are artist. I really believe Gaga can crank out catchy, party-ready hits very easily; she did it nearly effortlessly with The Fame. She's an excellent songwriter and musician and singer, which puts her way above most of her contemporaries, who tend to rely on writing teams and megahit producers for their success. Gaga is a self-run, self-driven machine. She's made many great songs in the past and she'll continue to make great songs; I think sometimes this fan base forgets that and gets caught up in chart positions and whatnot.
