I always find with any singer that some there songs seem to be pushed to the back and barely anyone talks about them, i think from Taylor the ones which i adore and are so beautiful and i think are some her best are..

A Place in This World
A Perfectly Good Heart
Cold As You
Stay Beautiful
Tied Together With A Smile
The Outside
I Heart Question Mark
Beautiful Eyes
Invisible
Mary's Song (Oh my my my)
Breathe
You're Not Sorry
The Way I Love You
Tell Me Why
Come In With The Rain
Other Side Of The Door
Superstar
Dear John
Innocent
Never Grow Up
Better Than Revenge
Haunted
Last Kiss
If This Was A Movie
Christmas Must Be Something More
Christmases When You Were Mine
Superman

EDIT
Best Day and Forever and always are a little underrated but best day has a video even if it is a bunch of home movies, forever and always has a release piano version and so i don't think it is that underrated, hey stephan was performed at Z100 as well as the best day so it played a little more.
Speak now is the name of the album and although not a single did have a tour video.
Enchanted well i think this one, is one the most talked about songs on the album and there for, is not underrated, i mean it's the music for the wonderstruck advert, and everyone wants it to be a single.

EDIT2
Unreleased ones- i would say all of them because not everyone has them but these are the ones that are mentioned even less and are amazing, and heard them so i know.

Brand New World
By the Way
Didn't They
For You
Need You Now
Never Mind- But Country Version
One Thing
Rain Song
You Do
Songs About You
Matches
Just Knowing South
Cross My Heart
Firefly

I think i got the right songs i just had to check my list, I'd Lie, Permanent Marker, Dark Blue Tennessee, What to Wear, We Were Happy, Diary of Me, Sweet Tea and God's Graces are kind of common so they are not on the list. Made Up You, Gracie, Making Up For Lost Love and Love to Lose are mentioned to much. The V2' are not great if anything they are overrated and made to sound amazing, but they are not. Also This is really happeing is SOLD so i wouldn't say it is underrated also shows that taylor will not release it.

Edit 3

Covers
Breathless
White Blank Pages
Viva La Vida
Baby Don't Break My Heart Slow
Silent Night
Last Christmas
Santa Baby
White Christmas


End of Edit
i think these are some of her best written songs but it seems like because they are not main stream pop then somehow they are never mentioned.
Anyone Agree