Too many people has grown up with Sonic Games (including me) so, it's fantastic that you have remastered Sonic 1, Sonic 2 and Sonic CD for mobile devices. However, too much people who have played Sonic 3 & Knuckles in their childhood would love a port of this game for mobile devices. Even better, like this you'll make more people who don't know Sonic but they have a mobile device meet Sonic games. 

In short, it would be a beautiful gesture for lifelong fans you ported S3&K for mobile phones and thus introduce new casual players to the fandom.