I think this is a more interesting question then tendoboy is being given credit for and I like imaging the world it suggests.
As has been pointed out, 3DO and CDi tried it and failed. But I don't personally think they failed because it was a bad idea, they were far too expensive and most of the games weren't as good as what we already had on SNES, etc. Jaguar and Sega CD failed at the same time too, and they weren't trying to create a universal format, they just cost too much and lacked games.
Ouya doesn't count to me because you have to go through their shop front and use their bespoke controller. So it's not like you could buy a game on your Ouya and transfer it to your Android phone (correct me if I'm wrong).
I don't really see Cross Play in the same way. The dev has to make 2 or 3 bespoke versions of the game, so it's more like those Triple play movie boxes where you get 2 discs and a download code isn't it.
I thought Onlive had a shot as creating a unified experience as it promised the exact same code on my desk top, lap top, TV, tablet and phone. Which it does do.... but it's a pretty terrible service. I guess a cloud service could deliver on that promise some day, but Onlive have proved pretty convincing that it's a very niche thing right now. Watching their big financial failure last year left me worried I had a £40 controller I could never use again (sold it and bought New Super Mario Bros 2. Thank you ebay) and convinced me that physical media is still the best choice because if the makers go bust I still have unlimited access to what I paid for.
I digress.
It's interesting to me that in music and movies there have been various attempts to create what we've essentially had in the console world for a long time: 2 or 3 formats all competing for dominance but managing to co exist. Remember when Philips DCC and Sony Mini Disc were battling it out and both wanted to replace CDs?
Or more recently when people actually paid cash money for HD DVD players?
Or those crazy VCR formats Philip developed in the 70s to compete with VHS and Beta?
Or when Laser Disc was the height of awesome over priced geek chic?
Fun huh!