Just going through a few...
Rihanna - Breakin' Dishes, likely next single.
Christina Aguilera - Slow Down Baby, WHAT is she waiting for? This has summer hit written all over it.
JoJo - This Time, good song much better than the past few singles she has been releasing.
Ashlee Simpson - Beautifully Broken, probably the only chance for another #1 and she blew it.
Danity Kane - One Shot, huge dance song but that is the Bad Boy flowchart, release two singles and you are gone.
Ciara - My Love, and it better be next single. I read somewhere it was.
Ciara - Hotline, could have been a killer dance hit.
Why weren't these hits?
Christina Milian - Say I, This song was a single--it was doing damn well until she got dropped from DJ, then EVERY radio station took it down.
Jessica Simpson - I Belong To Me, WHY? WHY? WHY? WHY? WHY?
Paris Hilton - Nothing in This World, I have no idea why this wasn't a hit. Yes, it is a Paris song, so what, it works. Of course (be honest) it didn't get airplay because simply put, it's a Paris song.
But CHRles is right, I'd say 90% of the time the record companies pick the right ones for important reasons.