Not a lot to say on this one, cosmetics vs. functionality.
This article is a little outdated but still fairly relevant in what it says. It misses out controllers such as that of the Sega Megadrive and the Brown box. From this article it is apparent that a lot of the changes are more cosmetic to get around patents than thought out additions to controllers. It suggests that the use of a joystick is now non existent, but in reality it has just been reborn as an analogue stick. The time of “conventional” controllers is over as the article states, although I dispute its claim that the wii-mote is the future of gaming. There is still a lot to be said for the old school controllers. They where primarily designed for comfort and functionality second. The likes of the wii-mote focuses more on its motion sensor technology than on the actual buttons. Despite the reliance on the motion sensing technology the technology itself is pretty buggy and half the time doesn’t work. The buttons are hard to press and in awkward positions. Controllers such as the 360 and PS3 controllers are still much in preference to hardcore gamers.
Another slightly outdated webpage which needs updating. This is a reasonably good representation of the progression of consoles. It misses a couple of consoles out of its list but it is a good general overview. This shows how functionality is slowly given less thought as cosmetic design is given precedence.