Genghis Khan by Miike Snow

Pretty much any Owen (Mike Kinsella) song.

Heaven Sent by Trophy Eyes

Gotye - Somebody That I Used to Know.

Nothing Better - The Postal Service

gotye - somebody that I used to know (techncially)

Jealous guy, Lennon

This kind of music is my jam.

A popular hit that's semi-recent...well I guess not anymore is "Pumped Up Kicks" which was about a school shooting but was written with this carefree tone that really makes it all the more deranged.

There's a band I listen to called HIM and they have a dancy 80s rock vibe mixed in with gothic music tones. Their shtick lyrically is playing with goth romance cliches so you get a lot of "I'll love you to death" kind of stuff. Other Finnish rock bands that were around in the early 2k have similar stuff (69 Eyes, The Rasmus, Negative) but it varies whether or not it hits what you're looking for.

I, personally, think a lot of post-grunge music does this as well. So Cold by Breaking Benjamin, Saferwaters by Chevelle, Deftones plays around with this quite a bit as well (I know they're nu metal but whatever subgenres are nuts).

You'll find it littered throughout a lot of other rock music as well but that's mainly a consequence of it having dark lyrics while trying to have a type of dancy vibe for commercial viability. I think the more esoteric you get in rock the more this goes away. Prog rock seems to be a good vein for this kind of stuff too (Tool, Pink Floyd, Rush) but they tend to flip through a lot of themes so it's hard to condense a single song into "happy but sad" in the specific way you're seeking.

Back to more pop stuff - Save Your Tears by The Weeknd is a good one. Maneskin's cover of Beggin' I feel does this as well.

First one that came to mind was this:

Okkervil River - Black

Wouldn’t it be nice and most of Brian Wilson’s other songs

Also "Always the Last to Know".

Except fuck you. That one’s kinda uplifting

I Know You Rider - The Grateful Dead

Going down the Road Feeling Bad - The Grateful Dead

I once heard The Dead referred to as the joyful bearers of tragic news. I thought that was a pretty surprisingly apt description

Hey Jealousy by Gin Blossoms

Shiny Happy People - R.E.M. it’s most likely about everyone being on Prozac in the early 90’s- “there’s no time to cry, happy, happy!”

The phrase Shiny Happy People is rumoured to have been lifted from a mistranslated CCP propaganda poster about the student protesters at Tiananmen Square which described the students as shiny happy people. …Meet me in the crowd…

Still Feel Like Your Man ~ John Mayer

I remember this song leaked well before the album came out, and I was excited for the album to tell me what he was actually saying. I buy the album, and the lyrics literally say "my ... girl." Biggest troll ever.

The entire discography of The Cardigans, starting with their biggest hit Lovefool.

People Who Died by Jim Carroll Band

Scatology Ingurgitation by Taint Gobbler

Bye bye Love - Everly Brothers

I Kill Giants by The Naked And Famous.

https://youtu.be/1I56yYHxP2k

Mad world - tears for fears

Casimir Pulaski day - sufjan stevens

PARAD(w/m)E

Lily Allen - LDN

Actually, any Lily Allen song.

90% of Smiths songs.