The 15 Song Album collection:

so at least narrow to broad genres?

eg, jazz/ blues/ "classic" rock (and the 27 zillion sub categories thereof) , new-age/ambient


etc

how about for fun - your favorite & and your favorite overplayed (could be the same tune)

Inagaddavida
Stairway to Heaven

but seriously, a single favorite? - kinda like asking - Glenmorangie or Booker's Small batch?
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp (this time they aren't in ironic mode!)

Of course plenty of song titles (especially from British bands) seemingly or purporting to be about happiness are actually the quite the opposite.
For instance "Wonderful Life" by Black.
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
10 - Dont Worry Be Happy - Bobby Mc Ferrin
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
10 - Dont Worry Be Happy - Bobby Mc Ferrin
11 - I Feel Fine - The Beatles
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
10 - Dont Worry Be Happy - Bobby Mc Ferrin
11 - Lookin' Out My Back Door - Creedence Clearwater Revival
 
fixed it

01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
10 - Dont Worry Be Happy - Bobby Mc Ferrin
11 - I Feel Fine - The Beatles
12 - Lookin' Out My Back Door - Creedence Clearwater Revival
 
01 - Reason to live - Kiss
02 - Jolly Mon Sing - Jimmy Buffett
03 - What a Wonderful World - Eva Cassidy
04 - Mr E's Beautiful Blues - Eels
05 - Life - Mika Nakashima
06 - 59th Street Bridge Song (Feelin' Groovy) - Simon & Garfunkel
07 - Alive - Goldfrapp
08 - I Feel Good - James Brown
09 - Reasons to be Cheerful, Part 3 - Ian Dury and the Blockheads
10 - Dont Worry Be Happy - Bobby Mc Ferrin
11 - I Feel Fine - The Beatles
12 - Lookin' Out My Back Door - Creedence Clearwater Revival
13 - Life's Been Good - Joe Walsh