All Star by Smash Mouth, obviously.

One of my favorite little details of Blood and Wine, Witcher 3, is random people humming or singing small refrains of modern pop songs like the Beatles, implying these tunes are exactly what you're asking about.

I have never heard of or heard Greensleeves until today

One thing people might not realise, is that memorable old music can come and go. Until someone recorded a successful rendition in the 60's, Cannon in D had been forgotten for centuries. Now it's almost synonymous with wedding music, and seems completely timeless.

It's possible everyone will be crazy about 1919's El sombrero de tres picos in 2450, and (with this all being indistinct distant history) will picture us in 2024 playing it on boombox at a 2050's-style holo-orgy.

Today's Greensleeves

7 nation army by the white stripes. It gets played after a goal is scored in football stadiums across the world.

Happy Birthday has the kind of universal recognition you'd be looking for. Maybe in 300 years there'll be a lyrical shift towards something more interesting. I know multiple versions of Greensleeves. The Cuckoo is the other song that I can think of with a long history. The wiki article doesn't fully capture it. I'll stick something in here later.https://en.m.wikipedia.org/wiki/The_Cuckoo_(song)

Belgian techno anthem Pump Up the Jam by Technotronic is one for the ages. Some say it has always been with us.

Here Comes the Sun. Simple melody, timeless lyrics, and it's the most-streamed Beatles song out of an already strong and memorable catalog.

It's...

PEANUT BUTTER JELLY TIME PEANUT BUTTER JELLY TIME.

Chumbawumba Tubthumping.

How many 1700s drinking songs does anyone know the tune of today? Well, there's "To Anacreon in Heaven", better known as "The Star Spangled Banner".

"Aura Lee" is from the 1860s, but the tune is better known today as Elvis's "Love Me Tender".

Not sure about today's, but I think the one from the 18th century is Ah! vous dirai-je, maman, better known in English as Twinkle Twinkle Little Star or the alphabet song.

You won't like the answer, but I'll tell you anyway.

It's The Macarena, by Los Del Rio.

Creep by Radiohead, imagine how much that would annoy Thom Yorke.

Happy Birthday, Pop Goes the Weasel, Auld Lang Syne, Here Comes the Bride are obviously here to stay. Lots of Christmas music has potential as well: Jingle Bells, and POSSIBLY Feliz Navidad by José Feliciano, as well as All I Want for Christmas is You by Mariah Carey.

But I also think Barbie Girl by Aqua has a decent chance of being practically universal. In that vein, maybe the Hampster Dance too, but idk. Dragostea Din Tei?

I think the real answer though is that most of the popular songs are probably ones that are connected to specific uses outside of the song itself. Pop Goes the Weasel is used in like, every pop-goes-the-weasel type toy, and even in movies when something scary is about to pop out at you. Happy Birthday is literally sung at every birthday. (That reminds me of For He’s a Jolly Good Fellow as well.) Auld Lang Syne is a popular New Years song across the world at this point. Here Comes the Bride at every wedding, etc. Maybe National Anthems will also hold the test of time, depending on if the nation lasts long enough and doesn’t change its anthem.

The point is, if it’s a practical and traditional tune it’s more likely to last, I think.

Oh. I forgot Reveille which is the military wake-up call bugle song lmao

Green Onions

Based on what I hear playing, my money is on Mr. Brightside.

Gershwin's Summertime is my real answer. It has been covered by so many artists already, it might keep going.

O Fortuna, Carmina Burana.

The poem was written in the medieval period, but finally set to music in 1935-1936. It still took till the 1970s to be used in TV/Film and became so widely used, it is now known as the most overused piece of music in film history.

Fly me to the Moon - Frank Sinatra

Simple, yet very recognizable melody. Easy to whistle, but could also be extended to a whole orchestra with vocals.

What? "Baby Shark" hasn't been mentioned here yet?

Define "today"? My first pick would be Yesterday, but that's about 60 years old already.

the entertainer by scott joplin

Oh this is easy, but you may not thank me for it. Hum, whistle or sing, anyone near you will do the same after a minute or so. It's timeless and it even has it's own website

I give you Lipps Inc. - Funky Town

Bohemian Rhapsody

As much as I want TiK ToK by Kesha to be a recognizable tune in half a millenia I know that's not happening. Personal Jesus by Depeche Mode is one of the most covered songs of the past 50 years so that very well may become immortalized through diffusion alone. There's a couple dozen jazz standards that could have that kind of staying power as well, especially considering their ubiquity in performance repitoires and books of sheet music.

"I like to f*ck" by Tila Tequila.

Essentially the same lyrics, even.

The nes super Mario bros overworld theme comes to mind. People who have never played a Mario game in their lives know that tune.

Hey Ya

Bella Ciao