Research: Gaming - How has it evolved?

I remember to this day playing Super Mario Bros. on my NES when I was just a kid and how entrancing it was.
The NES only ran at 8-bit graphics, meaning most game characters were built from a small number of coloured blocks, which ended up just about resembling what they should look like.

Super Mario Bros. 1985 NES

I am going to use Super Mario Bros. as an anchor point for some of my investigation.
In Super Mario Bros. you play as Mario (or Luigi with two players) attempting to rescue the Princess Toadstool from Bowser. Enemies include Koopa Troopa's, which are essentially tortoises, and Goomba's, which are walking mushrooms. When 'killed', the Koopa's go back into their shells when jumped on, and the mushrooms are squished. Although the latter does sound horrific, there is little-to-no violence at all. When Mario is touched by one of these, he doesn't get hurt, a simple animation of him flies down the screen.
Mario games today are the same.

New Super Mario Bros. 2009 Wii

Take away the fact the image above is graphically superior (I will get onto that soon), and the fact Mario is huge (due to collecting a power-up) it is essentially the same. Koopa's and Goomba's present, the world looks the same, Mario looks the same, and the innocence is still there.