Until Sonic CD, Sega's iOS ports of its retro licenses had been travesties. Poor performance and ropey controls demonstrated that Sega either didn't know how to do justice to its classic titles, or simply didn't care.
The reason why Sonic CD is so different? Because Sega didn't really make it. This version is one that Sega co-opted from a chap called Christian Whitehead, and amounts to a complete re-writing of the Sonic CD code to ensure it runs at a rock-solid 60fps and offers controls that work properly with the touchscreen. The result is a fantastic platformer.
To further sweeten the deal, Sonic CD - the version of Sonic released for the ill-fated Sega CD back in 1993 - is considered by many to be the best of all the Sonic games. Its existence is a mixed blessing for Sega, as it makes us want the publisher to create proper versions of Sonic the Hedgehog and Sonic the Hedgehog 2 using the same method employed here. If Christian Whitehead can do it, why can't one of the App Store's most well-known names?
One of the best platformers for iPhone, and the only one to date that does the Sonic name proud.