Firework. I don't know if I'd consider it overrated though? It was EVERYWHERE...but at the same time it was mocked by pretty much, everyone. Whatevs, my vote goes to that disgusting plague of a song.
I loved firework when i first heard it but by the time it came to the 4th month and people were still singing it on the way to school I realized how overrated it was its a good song though