To be honest, when comparing the songs in LBT to music I would listen to on a regular basis, LBT songs score fairly low. This is due to a number of reasons, some of which are objective, some of which are subjective. I will not be able to properly explain exactly why this is very clearly but am willing to try to answer any questions.
These ratings consider the appropriateness of the song for the scene and atmosphere in the film, how well the music fits with the song, how well the song is produced and the overall performance of the song. These rating are intended to be as objective as possible. My scoring system is as follows:
10: The film receives large amount of benefit from having the song. The song is very appropriate and well-engineered.
5: The song has little effect on the film's quality. Song is fairly appropriate but lacks attributes which would have made it improve the quality of the film.
0: The song reduces the quality of the film very much due to its very poor design.
So it's like a balance beam or see-saw:
_______0-------------------------5----------------------10
-----Negative------------------Neutral----------------Positive
These ratings are my Objective ratings. I tried to eliminate as much personal opinion from these as possible. It would be interesting to discuss these in more detail
//------------------------------------------------------
II -The Great Valley Adventure
Peaceful Valley (Opening version): 8
Eggs: 6
You Are One Of Us Now: 8
Peaceful Valley (Full version): 7.5
III - The Time of the Great Giving
When You're Big: 6
Standing Tough: 6
Kids Like Us: 8.5
IV - Journey Through the Mists
Grandma's Lullaby: 7.5
Who Needs You?: 3.5
It Takes All Sorts: 8
V - The Mysterious Island
Big Water: 6.5
Always There: 9.5
Friends For Dinner: 5
VI - The Secret of Saurus Rock
The Legend of the Lone Dinosaur: 4.5
Bad Luck: 4.5
On Your Own: 7.5
VII - The Stone of Cold Fire
Beyond the Mysterious Beyond: 8
Good Inside: 4.5
Very Important Creature: 8
VIII - The Big Freeze
The Mad Song: 6
Family: 8.5
The Lesson: 7.5
IX - Journey to Big Water
Chanson D'Ennui: 7
Imaginary Friend: 6.5
Big Water: 6.5
No One Has to Be Alone: 10 (I have a hard time finding fault in this song)
X - The Great Longneck Migration
Adventuring: 8
Me and My Dad: 6
Bestest Friends: 9.5
XI - Invasion of the Tinysauruses
Creepy Crawlies(1): 4.5
Creepy Crawlies(2): 4.5
Girls & Dads: 1.5
If Only: 7
Stupid Stompers: 5
XII - The Great Day of the Flyers
Things Change: 9
One of a Kind: 6
Flip, Flap, and Fly: 7.5
//---------------------------------------------------------
And these are my subjective opinions of each song, using the same rating system. Check these out if you're curious

II -The Great Valley Adventure
Peaceful Valley (Opening version): 8.5
Eggs: 5.5
You Are One Of Us Now: 7
Peaceful Valley (Full version): 7.5
III - The Time of the Great Giving
When You're Big: 6.5
Standing Tough: 6.5
Kids Like Us: 8.5
IV - Journey Through the Mists
Grandma's Lullaby: 6
Who Needs You?: 5.5
It Takes All Sorts: 7.5
V - The Mysterious Island
Big Water: 7
Always There: 9
Friends For Dinner: 4
VI - The Secret of Saurus Rock
The Legend of the Lone Dinosaur: 4.5
Bad Luck: 3.5
On Your Own: 7.5
VII - The Stone of Cold Fire
Beyond the Mysterious Beyond: 9
Good Inside: 3.5
Very Important Creature: 5.5
VIII - The Big Freeze
The Mad Song: 3
Family: 8.5
The Lesson: 8
IX - Journey to Big Water
Chanson D'Ennui: 8
Imaginary Friend: 3
Big Water: 7
No One Has to Be Alone: 10 (I have a hard time finding fault in this song)
X - The Great Longneck Migration
Adventuring: 8
Me and My Dad: 5
Bestest Friends: 9.5
XI - Invasion of the Tinysauruses
Creepy Crawlies(1): 4
Creepy Crawlies(2): 4
Girls & Dads: 4
If Only: 7
Stupid Stompers: 5 (if "Creepy Crawlies" is present)
0 (if "Creepy Crawlies" is not present)
XII - The Great Day of the Flyers
Things Change: 8.5
One of a Kind: 4
Flip, Flap, and Fly: 6