As for the poll, Sabbath and Zepplin cannot be called rock. They're original heavy metal. Nirvana was grunge and The Ramones were punk. Oh and I and many others consider Pink Floyd to be progressive rather than rock.
It all comes from Rock, that is the root, and Rock comes from a fusion of R&B, Blues, and what was once called "hillbilly" music, and later became Country/Western. There are probably about as many 'genres' of rock as their are exceptional bands, as that has become the hallmark of excellence in rock music... being innovative and inspiring new sounds. Rock has such a wide range, it is really hard to pick the best "rock song" of all times... it's like picking the best song of all times... there are so many variables and so much to choose from.
I was disappointed in the selections, they seem to be done off the top of the head, without much considerations for many great entries...
Purple Rain- Prince
I Want to Rock and Roll All Night- KISS
Thriller- Michael Jackson
Nights in White Satin- Moody Blues
Bohemian Rhapsody- Queen
I can think of at least two BETTER songs for The Beatles and Stones...
A Day in The Life- Beatles
Satisfaction- Stones
Some other honorable mentions for "greatest rock song" are:
All Along the Watchtower- Hendrix (written by Dylan)
Hotel California- The Eagles
Smoke on the Water- Deep Purple
Won't Get Fooled Again- The Who
...I could do this all night!
The thing I find fascinating is how the conversation here seems to reveal individual tastes in music, and this makes these sort of lists subjective. I happen to have a very wide appreciation for music, there is very little that I don't appreciate, especially live performances. Anything from Celtic, Reggae, Zydeco-style, Alternative, Indie, Folk... Those are my faves, but I can appreciate ALL music, it is the universal language.