Look i have a PS3 aswell as my PC but my Fiancee uses that for guitar hero and i use it for racing games(got it for GT5, still waiting for that game) and blurays. But i dont like the fact that a games performance is beeing held back by a console. Sorry if i am standing on a few toes here but jees that hacks me off. Maybe they should just make the pc version to its full ability. The consoles are limited so i can understand that but a PC is not. So why limit them?
The are a few reasons why. It largely has to do with game content, specifically it being REALLY expensive to develop two sets of content for PC/consoles.
A quick example, higher poly counts on 3D models requires more GPU processing power to render. Current gen GPUs (5000 or GTX 400 series) can handle lots of high poly models quite easily, BUT, the older console GPUs don't handle that nearly as well, so lower poly models are used. Creating and shipping two sets of models can become expensive very fast, so better to use the lower poly ones. Texture resolution also comes to mind. A lot of console to PC ports tend to come with low res textures developed for the console version, leaving it up to the community to create their own high res texture packs.
Another example that has a direct impact on gameplay is processing power. AI and pathfinding are extremely taxing on the CPU and as the amount of onscreen units increases, the CPU cost increases exponentially. Console CPUs are actually quite good, they are certainly old but they have decent processing power considering how long ago they came out. The real killer though, is most games leverage a substantial chunk of the console CPU for graphics. Basically, only have a few units on screen with acceptably AI, or a mass of units onscreen that are near retarded. Do developers create completely separate game scenarios to leverage the extra CPU power on the PC? Once again, becomes too expensive.
At the point you are creating separate assets and gameplay for another platform, it may as well be an entirely separate game.
A lot of what I've mentioned here, particularly around processing power is why for a long time hardware progression drove forward innovation in gaming. We've kind of hit a point of stagnation now.