I think the PC will go (and is going) through a similar phase as the Amiga was going through during its life cycle.
The low-end Amigas were capable of running a huge library of great quality games, for developers it usually made far more sense to produce games which ran well on low-end hardware as well as being compatible but taking very limited advantage of high-end more expensive Amiga hardware.
Currently every PC sold out there is capable of handling 99% of the tasks most people are looking for in a PC, there are 100 millions of PC gamers out there, but people who own a machine to get the most out of a game like Crysis (and don't pirate games) is a very small percentage of this. The best selling PC games are actually usually the less demanding ones, sometimes still using less advanced not very heavily multi-threaded game engines.
On the Amiga only a handful of people upgraded their Amigas to play games like Quake, Wipeout 2097, Heretic 2, Earth 2140, Shogo, etc or good Amiga exclusives like Alien Breed 3D II, Foundation, Napalm, T-Zero Genetic Species, etc. Simpler less demanding games everyone could play (on 7-14 Mhz Amiga hardware) like Slamtilt Pinball, Capital Punishment, Phoenix Fighters, etc performed better sales wise. In the end this nearly killed the Amiga gaming scene and Amigans are now mostly stuck to playing new versions of Amijeweled and linux game ports. The Amiga lost games like Grand Theft Auto to the PC, Team 17 released future versions of Worms on other platforms, future Lemmings versions would not hit the Amiga (the Amiga original supporting 2 player mice combat was the best version) and so forth.
Of course the PC had one big advantage over the Amiga situation, that's the resource hog Windows, many people will eventually buy a new PC as past Windows releases are being phased out. Likewise people are now upgrading classic Amigas or buy new Amigas to be able to run AmigaOS 4.1 properly.