1. Many phone tablet games compromise the controls due to the lack of button or stick controllers. They would actually be improved by a gamepad.
2. If a market exists then people will adapt the games to that market. It's not hard to imagine how many touch-only games could be altered in fairly minor to be D-pad friendly.
3. Developers will innovate new approaches to game input if the hardware is out there.
While it sounds nice to run the same game on a console and a touchscreen I don't see that working too well in reality.