Don McLean - American Pie (1971):
A true American epic, hence it always deserves consideration for any list of greatest songs of all time. The lyrics are some of the most poetic in a song, both in terms of rhyme and rhythm. Pairing the death of Buddy Holly with mentions of James Dean and others captures the "helter skelter" of the state of music, and popular culture as a whole, in the late 60s and early 70s as a "a generation lost in space".
Radiohead - Fake Plastic Trees (1995):
The video for Fake Plastic Trees makes the song, I believe; it is a song about the commercialism and technological development of the 90s. It was inspired by Canary Wharf, a heavily built up area of London, the song describes "her green plastic watering can/for her fake Chinese rubber plant/in the fake plastic earth/that she bought from a rubber man/in a town full of rubber plans". A pretty harrowing image of the present and the near future, as "it wears her out [like plastic products]".
The Avalanches - Summer Crane (2000):
This is probably the least well known song on this list, but it is on one of the greatest gems in music, the album "Since I Left You". The song is a mosaic and a scrapbook of various sounds, which makes it sound that several songs are playing at once. But instead of cacophony, a eclectic mix of beats and melodies. Even the limited vocals are chosen and edited in such a way that it makes them instrumental. Not to mention the last forty-five seconds are probably one of the most beautiful bits of music.
