"Any artist with a surplus of material would be advised to save it for the deluxe reissue or website giveaways. But, though it began as a quirk of formatting and became an often cynical marketing ploy, for more than 40 years the B-side could also be a way of thinking about music: a parallel universe of creativity." (The Pet Shop Boys B-side included in this article is totally new to me, and actually really good, make sure to give it a listen.)
And who can forget the B-side to the Dickies' cover of "Paranoid" - "You Drive Me Ape, You Big Gorilla?"
The remix also killed the b-side, instead of a fresh song you just got another version of the a-side.
I can name the b-side of every Jam single, they were all that good.
@LondonLee It's more of a transition than a replacement, at least depending on the music you're talking about. You get an Underworld single from the 90's and the A-side's the radio edit and the B-side's the extended club edit. Meant for different things, for all intents and purposes entirely different songs.
Oasis has better b-sides than a-sides (Definitely Maybe and What's The Story... notwithstanding). That always drove me crazy.