what are your five essential songs

Since classical wasn't excluded, and in fact the op's post included a classical selection:

"Nessun Dorma" -- Puccini's "Turandot"
"O Mio Babbino Caro" -- Puccini's "Gianni Schicchi"
"Alto Rhapsody" -- Brahms
"Un Bel Di Vedremo" -- Puccini's "Madama Butterfly"
"Quando M'en Vo' Soletta" -- Puccini's "La Boheme"

And a separate list for popular:

"My Cup Runneth Over" -- Ed Ames
"Both Sides Now" -- Judy Collins (original release only)
"Today" -- The New Christy Minstrels
"Tammy" -- Debbie Reynolds (laugh if you want to)
"Steve's Song" -- The Blues Project

Regards,
-- Al

Grateful Dead from Wake of the Flood "Attics of My Life"
Louis Armstrong "East St. Louis Toodaloo"
Beethoven "Fifth Symphony"
Santana from Supernatural "Maria Maria"
Jerry Garcia from Reflections "Catfish John"

Miles-"Attics" appears on AB, NOT Wake! You gotta get this stuff right.

In order:

King Crimson- 'Starless'
Kyuss- 'Whitewater
Uriah Heep- 'July Morning'
Blue Oyster Cult- 'Astronomy'
Yes- 'Starship Trooper'

I don't think any 5 songs alone can sustain me. I'd find another hobby.

But if I had to chose:

Epitaph - King Crimson
Suppers Ready - Genesis (at least its 20 minutes long....)
Man Erg or Still Life - Van Der Graaf Generator
Blue World - Moody Blues
Some Dylan song, not sure which ("Highlands" maybe, that's long too)!