I cant really think of many overrated songs because there are a lot of songs I dont like that other people do. However this is "commercial pop crap" that lots of people into rock music would agree with me on.
Nice to see another appreciator of animal collective btw.
Actually, I can think of one, Sweet Child of Mine by GnR. I like it as a song, the riff is one of the most recognizable in recent music but it was originally a string skipping exercise by slash, coupled with a cheesy poem axl rose wrote about his girlfriend. The outro "where are we going to go now" is literally saying "well how the fuck are we supposed to finish this?" and it is just way too overplayed.
As for underrated music I dont see many Leanord Cohen fans around nowadays, Bob Dylan is probably rated right where he should be, the velvet underground too, and The Grateful Dead are often overlooked when talking about good sixties music, though a lot of their songs i dont like, but the ones I do are masterpieces. Jefferson Airplane too for that matter. I also think Purple Haze was one of Hendrix' weaker songs, but i love to play it anyway. More fun to play than to listen too imo and the lyrics are good.
Edit: Shit i forgot about coldplay, middle of the road boring pop rock, but the hating coldplay club is rather large so that evens the overratedness out.