Well, i'll take a recent example for why i think PC gaming is worth it.
Team Fortress 2.
It is
miles better on the PC for one simple reason: Custom content.
The game ships with 6 maps. I have over 40 custom ones saved on my computer, and play a lot of them regularly. Most of them are just as good or better than the official ones, and
greatly expand the game experience.
Another example: Battlefield 2.
The community made mods were better than the standard game. Forgotten Hope 2, Project Reality, Point of Existance etc.
It's just better on the PC, along with a lot of other games. Flalalalatrategy games are always better on the PC because you get to use keyboard+mouse instead of dual analogue. Games like fighters and racing games are always better on the consoles. However the PC is the king for fps's.
However i am wanting to get myself a 360. I miss the days of sticking a game into the console and playing without any problems. But the PC is always where fps's and strategy games will be the best. Always

.