2. Sonic CD
If we can just turn your little cookie-cutter world upside down for a second here, the canonical version of Sonic CD isn't actually the Sega CD version at all. Though, admittedly, the 1993 original looked pretty special in 1993--particularly next to most Genesis titles, and particularly if you were young and undiscerning enough to fall within Sonic's target audience at the time.
Dig that game out now and all the new bits (such as Metal Sonic, in-game time travel and, ahem, Amy Rose) look a little less shiny, but are surprisingly innovative for the series. Still, it was starting to show its age, at least until a recent downloadable port, rebuilt for modern consoles and mobiles, is the game that actually plays as well as you remember.