Coldplay is my personal choice, but to be quite honest, if you're looking for timeless, rap and hip-hop have far more contenders than anyone else. Eminem, Nas, Tupac, Biggie, even The Roots will be remembered for a long while. They're icons of the 90s just as The Beatles are an icon of the 60s and Queen, AC/DC, Black Sabbath, etc were icons of the 70s.
EDIT - MC Hammer. As much for his catastrophic financial fuckup as for "Can't Touch This". He's an excellent representative of the early 90s.
I don't even like rap and hip-hop that much, but as far as history is concerned, they have the biggest names.