Music can only be counted as 'dad rock' if it is music that has failed to remain popular with younger generations, e.g. Dire Straits, The Yardbirds etc., whereas bands of the same era such as Led Zeppelin and The Rolling Stones would not count as their music transcends the generation gap and is still popular with younger people
Dude B: Wow man, really? Dad rock?
Dude A: Shut up. I can name 10 reasons why it's better than new age music.
Dude B: *Shuts up with a sheepish look on his face*
They also tend to have long titles.