Nothing will start a flamewar faster than asserting that the PC is "dead" or "dying" as a gaming platform. But I hope I can at least point out that the PC isn't driving the industry the way it used to without PC stalwarts exploding into a state of apoplexy. I know that PC doomsayers have been wearing sandwich-board signs proclaiming "THE END IS NIGH" since long before Duke Nukem ran out of chewing gum, and the platform still won't be dead when they release the next batch of Duke Nukem Forever screenshots in 2017. But while "death" is not an appropriate word for what has taken place on the PC, the platform's influence isn't what it used to be.
Ten years ago, the PC ruled the game store like the mighty T-Rex. The shelves were stacked floor-to-ceiling with PC games, PC peripherals and PC gamers - the exotic console stuff was all heaped along one wall. Now that setup is reversed. Long-time PC developers like id Software and Epic Games are beginning to see their PC efforts as secondary. Games are made for consoles first, and then (sometimes ineptly) ported to the PC as an afterthought. Yes, there are good PC games left out there. The PC platform lives on, but the glory days are over. And in the end, it was its greatest strength that led to a reversal of its fortunes: the GPU.
The main advantage of the PC as a gaming platform was that it wasn't actually a gaming platform - not on purpose, anyway. People had PCs, and with ingenuity it was possible to make games that would run on them. Consoles were (incorrectly) seen as toys for kids and teens, and few adults would run out and buy an N64 or a Sega Genesis for themselves unless they were already gamers. What non-gamer would go out and drop $200 on a videogame system just to see if they would like it? Consoles could bring kids into the fold, but usually not adults.
On the other hand, a huge portion of the population went out and bought computers because they had computer stuff that needed doing. The computers were general-purpose devices, so gamers and non-gamers had pretty much the same machines. Even the machine Mom used to check her email was capable of running the latest games for the first year of its life.
This made PC games the gateway drug for most adults. The curious non-gamer could take a demo or a game on loan from a friend, run it on their PC and undergo the metamorphosis that transformed normal, well-adjusted people into bleary-eyed gamers who stayed up until dawn playing Sim City 2000, Dungeon Keeper, or (God help them) Civilization.
When the mighty GPU came onto the scene it made a host of new effects possible, and the first batch of games to take advantage of the technology straddled the line between the hardcore and the average gamer. You could play the game un-accelerated for a passable experience, or you could pop in one of those fancy Voodoo cards and see better effects, more detail and faster framerates. Big titles like Quake II and Unreal Tournament worked with and without software acceleration so that people with off-the-shelf PCs could play right along with the big spenders and hardware fetishists. Better hardware meant the game would look better, but everyone could play. This situation was beautiful, ideal and completely unsustainable.