You can go into a store and buy a book, a film and the latest album from your favorite band and you don't have to worry about if they are compatible with your reading skills, your DVD player or your audio equipment. They only "culture container" that puts a restriction around what you can access are museums, but that makes sense since the objects exposed are unique and only and can't be on all museums at the same time, and require security and manteninance labors to be preserved. But this does not apply to games. And still we are forced to choose pay a museum ticket that costs between 250 to 600 $/€ to be allowed to just play a fraction of the existing games they have on display, and you have to stick to it until it stops working unless you have money to spare or you are willing to make a scrifice in your personal economy because you like games so much (what I did). How can so much people consider videogames art if the first choice you have to make regarding them is discriminating wich you won't play, even if you would like to? Would you imagine yourself crossing things out of a list like that with other media? "I bouth a phillips DVD player so I won't be able to see Warner movies" "I bought a Kindle so I wont be able to read P.D. James novesl" "I'm using Firefox, so making a gmail account is out of the question".
You see, this is the defining point why your approach simply doesn't work. Unlike books, music & movies, all of them can be re-iterated and compacted into alternative forms of devices as long as they can run their intended media from a fundamental level. It works because all of these mediums are PASSIVE.
Video games on the other hand, are at the opposite end of the spectrum. They are an ACTIVE type of entertainment, which means, you have to participate before the game can fully open itself up to the player. And unlike the other mediums, video games have a very specific type of requirement before a game is played - it is NOT the console but....
This is one of the factors that is blatantly overlooked when it comes to video games. The controller DEFINES how the game is played, and to have a singular monopoly on console-to-do-all would mean innovation and gameplay would be affected only catering to the least restrictive input system, in this case: the 360/PS3 pad.
In your case: Touchscreen. Why? Because theoretically speaking, most smartphones/tablets could pack enough power to run every game from the Atari all the way to the PS2 (possibly some very early PS3 launch titles). It is the closest possible factor that fulfills your criteria - but think about it - we are already seeing emulators running well in those devices but why did it not encompass the masses the same why traditional consoles would? Put it simply,
there is no universal input to play all the games even if you had the technology to run them. Having a 3rd party device would only segregate your audiences, worse, you have to don't have a target point to which you can design your game. Until a system that can allow such a market to thrive, there is no way it can possibly work well for both consumers & developers.
This is why we need different systems. Each of the system provide an experience differing to the others changing gameplay and gamestyle. The only motivation for a company is to deliver the best possible experience on their platform whether it's providing a service (XBL/PS+) or introducing a unique way to play (3DS/NDS/Wii). No one console, not even the PC is capable of having the backing required to push that innovation.
