In those 5 years Pc's games come out with better Visually stunning games while consoles visuals remain the same. That's not true.
Look at comparison pics between Forza2 and Forza3 on the Xbox360; you'd swear they were on different generation consoles. Consider now that Forza4 is coming out on the 360 as well and looks better
again.
There is one very important and lucrative aspect of consoles, from a developers perspective, that a lot of people completely ignore - they're static. First thing that comes to peoples minds when i say that is "that's the problem, they're old hardware" and whilst sure, that is a fact, it doesn't have to be a
problem.
Consider custom graphics configs for Crysis for example. There's hundreds of them available to download, all offering different settings, all created by different people, all optimised for the system configuration that the creator of the config was using. That last part is the important part. People create these configs and they tweak and skew the settings that give them the best visuals for the best performance - this is called optimisation.
Let's now imagine that every PC gamer has a top of the line gaming rig, all the same configurations (eg; i7 + GTX580, 4GB RAM). Now, the first config is created for Crysis and it looks pretty great and it runs ok. Now, two months after Crysis is released, someone has spent this time tweaking a config to give better visuals but to optimise the settings for better performance. Visuals are a tiny bit better and you get an extra 5fps - Great! Fast forward 2 years and there has been hundreds of configs created, tweaked and mastered; Now Crysis looks far better than it did and runs at almost twice the speed.
Why, you ask? Because people have gotten used to their i7 + GTX580 + 4GB RAM setup. They know it's limitations, they know it's strong points. They know they can have up to 500 trees on screen without much of an issue because the GPU has the processing power. They know they can only have 20 particle effects on screen because otherwise the CPU starts to suffer. They know they can have 2048x2048 textures because the vRAM is sufficient and they know they can stream up to 3GB of texture data because the RAM is sufficient. They know the setup, and the more time they spend on this setup the better they can make it. They know where it can be pushed harder and they know where they need to take it easy.
^ The above is the result.