STEAM was just the first to do it best, had it not been Valve another company would have taken the spotlight whether that be Stardocks Impulse
(No longer actually owned by Stardock, go figure!) or Paradox's Gamergate or a whole slew of other digital distribution services like Direct2Drive. And hell, STEAM was initially reviled by gamers... no really, it was and I was among them. The absolute mess that was STEAM's launch along with Half-Life 2 was disastrous, the damned thing didn't work. Thing is that HL2 sold well enough that it guaranteed a stable community, a community which expanded as Valve continued to support their service by releasing new games for it as well as making it suck less so it could eventually become the monolith it is today.
So no, STEAM didn't 'save' PC gaming, it was simply at the forefront of the 'digital distribution revolution' that's since overtaken PC gaming to such an extent that many PC games aren't even being released retail anymore and major developers and publishers consider it their major source of revenue on the PC platform.
LINKY.
Digital Distribution on the PC has become so big that even the big boys are trying to get in on the action now. Ironically even big boys like GameStop, one of the companies whos neglect of the PC platform at retail helped drive the change to digital distribution. In their haste to promote used games sales
Which by now represent over 50% of the companies profits since they don't have to share with developers or publishers they all but abandoned the PC platform in which used games sales were difficult and often impossible. But NOW that they see there's profit to be made online they want in again and have bought Impulse from Stardock.
Pity, I liked Impulse. Hope Stardock got a nice cheque for it at least, because GameStop wont be getting my money, that's for damned sure.
ANYWAY, no, STEAM didn't save anything. It's just really good!... I hope someone reads this or I'm gonna feel silly.