"Freebird" and "Stairway to Heaven" followed a critical formula of 70s rock anthems: you basically take two unrelated songs and tack them together, and hopefully have an extremely long guitar solo in there somewhere, too.
"Starship Trooper," by Yes, also followed this formula, with the delightfully pompous added touch of being divided up into "movements" like a classical piece.
And then of course there was "Feeling That Way / Anytime," by Journey, which really deserves more acclaim for 70s cheese-rock anthem status than Freebird does.
For the 90s, I've long believed that "I Am The Resurrection" by the Stone Roses is that decade's "Freebird."
and heh... one thing I'll never stop laughing about is my sister's Junior High School yearbook from 1980, where they note that "the biggest debate of the year was which song rocked more, Freebird or Stairway to Heaven."
Ah, if only that were the biggest thing we had to worry about now....