Wow. What a crazy choice! I had to go with Nirvana, because I am a child of the 90s and that is by far the best song of the decade. It really brought through the grunge movement, and alternative rock, and I really don't think a lot of my favorite bands would have ever gotten radio play if it wasn't for Kurt Cobain and the rest.
Strawberry Fields was up there, as was 32 Flavors, but Nirvana is clutch for Gen Y, so I can't not vote for them, ESPECIALLY that song.