1. Complete Backward Compatibility
Is it really that hard to do this? I think that they don't even need to have slots for past games. I have plenty of old Nintendo games and Playstation games that I'd love to play on my Wii and PS3. Problem is, the Wii can only play Gamecube games while my PS3 is one of the models that can't play past games. My proposal to fix this is to have a fairly complete library online of games from past consoles. This being pretty much done anyway, all that's left is typing in the product code and you get a free download of that game. Fair, simple, and people will have more reason to buy a second controller. (And if they're real cheapskates, they could charge 10 cents. I wouldn't mind.
2. Small Size and Ability to Plug into Your Computer
Ever since the beginning of the Gamecube, I had wanted to console games on the go. So I bought one of those tiny TVs that attach to the top of your Gamecube and plug into the car. Now this wasn't TOO bad until I found that the screen is thin plastic that scratches, there are way too many parts that get lost, and it turns off when the car gets turned off. This could all be remedied by simply having a USB cable attached to a relatively small console (Wii sized is good) and an application that turns your laptop into a TV. Never again would you have to forfeit console games on a long trip.
3. Bringing Back the Nintendo Seal of Quality
Not just Nintendo, mind you. Sony and Microsoft need to make their own seal of quality. Far too many crappy or quick-cash-in games are being allowed to run free on today's consoles. Now that I think about it though, Nintendo has been allowing the most atrocities recently. Each game on the next gen consoles must be thoroughly tested and be made sure to not get below a 50% score on Metacritic. If they don't meet quality standards, then the game will be sent back or canned. Of course, it will cost a lot of money to be constantly making high-quality games, so I suggest that Sony, Microsoft, and Nintendo should give a flat amount of money to every game that passes the quality test (on top of profits of course).