I think we need to acknowledge that no other bands have a tune comparable to "Stairway to Heaven" in their respective catalogues. Even if you look at big bands like The Rolling Stones and The Beatles, you won't find a song that dwarfs all the band's other singles.
Now, if you mean, 'what is so-and-so band's ultimate song', which "Stairway to Heaven' symbolizes in the Zepplin song lists, then you could make a seriously argument for every band that every existed. "Beautiful Day" is by far the most widespread U2 single to date. More people know this song, than "With or Without You", "One", and "Mysterious Ways" combined.
Now, if you mean, 'what is so-and-so band's ultimate song', which "Stairway to Heaven' symbolizes in the Zepplin song lists, then you could make a seriously argument for every band that every existed. "Beautiful Day" is by far the most widespread U2 single to date. More people know this song, than "With or Without You", "One", and "Mysterious Ways" combined.