Like a Virgin and Papa Don't Preach are her classics. The rest of her 80's singles are also decade staples and are known by people who lived through that era.
Madonna doesn't have one signature hit but she has like 10 songs that share the space of what, per se, Cyndi Lauper's hits occupy. And then more beyond that.
I think it speaks volumes how everyone has a different opinion on what Madonna's classics are. When you have a large catalogue of worldwide hits it's hard to pinpoint what's deemed a 'classic' and what's not.
It's kinda weird how Whitney and Celine have a bigger classic than any Madonna song, while Cindy has two (!) Mariah has no global classics, and I'm not even gonna start with Janitor
Tbh when I was telling my friends I was suprised that LAP was so good they asked me if I meant like a virgin.
Idk if it's a classic although it definitely deserves to be.