[Jasonconfused]

I'm not suggesting that any artist that gets mentioned would have been bad if they were around any other time, just that the time period they were in was extremely important to their success. I guess another way of asking would be, which artists have been the MOST relevant?

Immediately, one that comes to mind is Nirvana. People were tired of the 80s glam metal and wanted something more real. (On a side note, I actually enjoy some glam metal)
Also, to a much lesser extent than Nirvana, but possibly thanks to Nirvana, Pantera! They were the only really heavy metal band of the 90s that was able to make it big. The reason being that grunge had pretty much killed off any large-scale interest in metal.

[Defago]

The Beatles.

EDIT: I read the question wrong. I guess Talk Talk and Slint were essential to post-rock. Probably there wouldn't be any without them. I'm also pretty sure krautrock had more influence than people seem to think on the development of music through the decades.

[L Lawliet]

Any band that ever did anything "original"
_________________
She's dead, wrapped in plastic.

Justice is not a frivolous thing, Simpson. It has little if anything to do with a disobedient whale.

[Kiki]

Pretty much all bands and artists were right people in the right place.

[Jasonconfused]

I don't necessarily think that any artist that did something original was successful due to their relevance. I'm talking more about artists that were culturally necessary. There are a ton of bands that have been original, musically, but how important has that innovation been to the overall times or the culture of people of that time in general? There have been a ton of great artists but not all of them have been NEEDED.

[Borve Baunehoj]

Pantera were only important to the process of creating nu metal

[Secondsoul]

Nirvana were a breath of fresh air. As were The Smiths when they burst onto the scene in 1983!

[sheep21]

In their day Blue Oyster Cult were pretty original and important. Now hardly anyone knows them and they have crap music, so why would anyone?

[thejoj96]

If many of the shitty indie folk/indietronic bands of today (these bands are a minority in terms of shittiness) were from a previous era, they would be forgotten and those who remembered them would hate them. So those artists are important due to their time period. On another note, if Kraftwerk (love their music) made their music today, they would be considered really bad. It's because of their time period that they are so acclaimed. I would still like their music though.

*None of this information can be proven, this is just a hypothesis

[Jasonconfused]