Interesting piece of news here, The Sonic Stadium found out that a sonic game was proposed for the iPhone. It's called Sonic Motocross! They even found this concept art done by illustrator Eric D Simmons-
NOTE: That is not the Boom version of Sonic, note that he does not have bandages, or the brown scarf, and it's quite common to make the mistake of coloring his arms blue.
It was discovered in hisresume (jump to page 4) and the source of the art work was found here .. The game was being developed by 2XL Games. However the game never saw the light of the day, and there's guesses that it would clash with two other mobile games, Sonic and SEGA All Stars Racing and maybe it's sequel, Transformed. (Also, it's been stated that it may have been developed between 2009-2013).
What do you think? Would you have liked to see Sonic riding a motocycle in the game?