The first thing that you notice when you first play on one of the current generation of gaming consoles (By which I mean Dreamcast and Playstation 2), is that they're really, seriously, fast. Games run at a constant frame rate, there's no jerkyness at all, and games rarely slow down regardless of how much stuff is on screen or however many people are playing.
By contrast, the majority of PC games can sometimes appear slow, unstable and jerky depending
on your hardware, what else you've got installed, and of course what day of the week it is.
For example, compare the PS2's "Killer App", Gran Turismo 3 with a roughly-comparable PC game Porsche Unleashed. Graphically, GT3 is simply so far ahead of what's been done with PC technology that it's stunning. Porsche Unleashed is also an outstanding game, but on my 1Ghz PC with GeForce 2mx, it's nowhere near as graphically impressive as GT3 either in terms of detail or raw performance.
People quite often ask why this might be, when PCs typically have a clock speed of 5 to 10 times faster than current consoles. In a word, it comes down to one thing- Optimisation. On a console, the hardware is optimised for the absolute best compromise between price and performance at a given time. The OS and development libraries are then optimised for the specified hardware and finally the game is optimised to make the best possible use of everything below. Everything is fine-tuned to perfection with consoles.
In a PC environment, this just doesn't happen. At the hardware level, thousands of different combinations of motherboard/cpu/graphics card/sound card/network card/monitor can be connected together to make "A PC". Almost no two are exactly the same, unless they happen to have been supplied by the same large PC manufacturer during the same week.
This creates a problem for the OS developers. Whichever OS you might choose, it has to support all possible combinations of hardware, which means that it has to contain a lot of redundant code, and if we're honest, a lot of untested and unoptimised code. There's a pretty good chance that a given device driver has never even been tested on your P3/P4/Athlon/Transmeta. What's more, the operating system has to provide a common interface to all applications regardless of what hardware it's sitting on top of.
Finally, at the highest level, the game will usually have been designed to run well on "A standard PC at the target release date". Developers pick a base specification and aim to achieve reasonable performance on it. Today, this might include a PC such as my own, or perhaps slightly faster. However, this is of course a moving target. Some games over-estimate the future performance of PCs (Flight Simulator 2000) and run quite slowly even on PCs a year or more after they were released.
I think that it will be interesting to see how the Microsoft X-Box affects this situation. Here we will have a console which is essentially based around 'off the shelf' PC components. Of course, its hardware and OS will be optimised far beyond what's possible with a PC. However, when people see fast games running smoothly on a console which is widely perceived as being 'PC based' I wouldn't be surprised to see the quality of PC games rising to meet expectations. Well, we can hope, anyway...
Ok, please consider sending me constructive criticism if you're downvoting. Have I missed something? Not enough detail? Too much detail? Perhaps it's because it might seem as though I hate PC games? (Incidentally, not true...)