Her albums contain so many gems which could have been real hits.

Worthy contenders:

Oops!...I did it again
Can't make you love me
What you see (is what you get)

Britney
Cinderella

Circus
Out from under
Amnesia

Femme Fatale
He about to lose me
Inside out

Inside Out.

Freakshow would have smashed the charts

Amnesia, Can't Make You Love Me, When I Found You, Touch of My Hand, Toy Soldier, He About To Lose Me

I agree although she usually has a decent run of singles there are so many ones that should have been either in place of others or just have been released for me:

...Baby One More Time- I Will Be There or Soda Pop to finish of the campaign.

Oops!...I Did It Again- What You See (Is What You Get), Can't Make You Love Me, Girl In The Mirro

Britney- Cinderella and Bombastic Love both should have been released instead of ILRAR just criminal.

In The Zone- Breathe On Me, Touch Of My Hand, shame the campaign was halted due to injury

Blackout- Radar should have come straight after POF, Toy Soldier and Freakshow and Why Should I Be Sad.

Circus- Unusual You in place of radar.

Femme Fatale- How I Roll, Big Fat Bass, Trip To Your Heart, Seal It With A Kiss, Drop Dead Beautifulo the entire album was chock full of potential hit singles but alas.

Unusual You.

Britney - Lonely
In the zone - breathe on me / I got that boom boom ( altho they were promo singles)
Blackout - the entire album tbh
Circus - Unusual You, Out From Under, Mannequin
Femme fatale - Inside out, He about To lose me, Up & Down, Scary, Selfish

Pretty much all of Blackout. I always thought Break the Ice was one of the weaker tracks on the album. Freakshow would have been a brill single.

I love most of Oops! as well. Particularly the last 4 or 5 tracks.

And Then We Kiss from her remix album is a brilliant track too. Would have also been a great single.

Lonely, Freakshow & Showdown.

Also B-sides that should have been A-sides:

Everybody- it has a smaple of Sweet Dreams how was this never put on the album let alone not released as a single.

Get Back- Another Great Song not included on Blackout with Huge potential.

Outta This world- A nice midtempo love song that would have slotted in nicely nd would have been good as the ballad released between all the beat heavy tracks.

I Will Be There [Radio Version]
Cinderella
Breathe On Me
Early Mornin' [Jason Nevins Remix]
Toy Soldier
Abroad
Unusual You
Amnesia
Quicksand
Inside Out
He About To Lose Me [Tour Version]

I agree so hard about all of those!

Also I find it baffling how she never included the ballad "everyday" on one of her albums simply beautiful my fave also I assume it was for / recorded for Femme Fatale?
She really does have so many great unreleased songs

Britney: Cinderella
In The Zone: Breathe on Me
My Prerogative: I've Just Begun (Having My Fun)
Circus: Shattered Glass
Femme Fatale: Up N Down, Gasoline, He About to Loose Me

Femme Fatale
Up n' Down
He About To Lose Me
Gasoline
How I Roll
Inside Out
Selfish (although it would have been compared to Rihanna's Only Girl a lot)

Blackout
Toy Soldier
Freakshow
Hot As Ice
Perfect Lover
Get Back
Heaven on Earth

Circus
Mannequin
Lace and Leather
Unusual You
Kill The Lights
Shattered Glass
Phonography
Trouble

In The Zone
Breathe on Me
The Answer
Outrageous (wasn't the release cancelled?)
The Hook Up

I'll think about the other albums later...

get back or toy soldier from the blackout album

Get Back!!

Outrageous was released, but only in certain countries and in a limited release iirc.

Anyway, I'd say Up and Down, Inside Out and (much as I dislike it) How I Roll were missed oppurtunities from Femme Fatale (over Criminal, which I love but wasn't a good single choice). Also I think it wouldn't have been a bad choice to release Shattered Glass or Out From Under off of Circus.

Mannequin is one of my favourite Britney songs ever, gutted Radar got released from Circus when there were so much better songs!

Before The Goodbye- LOVE this song!

I have one Britney song in my tracklists. Get Naked from Blackout, adored that album and In The Zone.

In The Zone:
(I Got That) Boom Boom Ft. The Ying Yang Twins
Breathe On Me
Touch Of My Hand

Blackout:
Toy Soldier
Perfect Lover

Circus:
Shattered Glass
Kill The Lights
Unusual You

Femme Fatale:
Inside Out
He About To Lose Me