1001 Albums You Must Hear Before You Die + 1000 Recordings To Hear Before You Die
I suppose a good place to start with Joy Division's "Unknown Pleasures" is the album cover. The shot of wavelengths from a pulsar (or a rotating neutron star) is among the most iconic pieces of album art of all time, and I'd go ahead and rank it among the best as well. The aesthetic value of the album ends there, and the real value begins here: "Unknown Pleasures" is the one album, more so than any other, that best represents the state of alternative music today.
This is a broad statement to make about a very broad genre of music, but I'll argue that it's true. First of all, there's Ian Curtis's voice. His delivery seems detached, but it's far from apathetic. So many artists have borrowed (intentionally or not) from Curtis's style, but have misunderstood it. It sounds lame but Curtis, for all his lack of ardor, felt everything he sang. If you don't believe it, you can read the lyrics into his suicide less than a year later. Many attribute his vocals to the formation of the goth movement of the early '80s, but Curtis never engaged in Bauhaus-style theatrics. I'd put him on par with a mellow Jim Morrison. He expresses what so many current apathy-dripping vocalists leave void.
Many instrumental aspects hail to the modern alternative music scene as well, such as the electronic chirps of "Insight" or aerosol can-as-rhythm in "She's Lost Control," but the group spends most of its time preceding the upcoming college rock movement. The "happy"-go-lucky riff on opener "Disorder" previews R.E.M., and "Candidate" could be a Nirvana ballad. Like Nirvana, Joy Division had grown under punk's wings, and the genre's influence shows in the faster, heavier numbers like riff-driven "Control" and "Wilderness." The post-punk genre is one that always confuses me, mainly for its disdain of actual punk. Joy Division is one of the bands deserving of the post-punk title, because it's one of the few bands that demonstrated what it learned from the title genre. Peter Hook's audible (and relevant) bass parts also suggest the dawn of college rock.
Even if the wide range of musical influences or Curtis's signature vocal style fail to convince you, the thing that tips Joy Division towards "most influential" is the band's place within pop culture. Which brings us back to that album cover. You can see that logo on T-shirts, on tattoos, on stickers. You can hear Division covered by bands from Dessau to Bloc Party to The Killers. Influence that widespread touches so many bands without them realizing it.
There's no way to trace what band has influenced more than another. And it's a tad conceited to claim just one group is that act. But between the combination of Joy Division's musical style, lyrical themes and overall recognizability, I would wager that it's a solid bet for the most influential band upon modern alternative rock. This is definitely a point I'd be willing to hear your opinion on. In the meantime, "Unknown Pleasures" is a great album regardless.
INTERESTING FACT: "Unknown Pleasures" was no. 2 on the first-ever UK Indie Chart. No. 1 was the equally classic (sarcasm) "Dirk Wears White Sox" by Adam and The Ants.