The problem with mining the rich and varied history of the Sonic the Hedgehog franchise for Sonic Generations is that history includes this red and black jerk-off right here. For some, Shadow is a welcome addition to Generations. For others, he still signifies the looming death of a beloved series.
Shadow will appear as one of Sonic's rivals in Generations, one of our heroes legendary enemies battling him on the stage of hedgehog history. Let's hope he doesn't bring a gun. If I had to pinpoint the moment the Sonic franchise stopped feeling like the Sonic franchise, Shadow the Hedgehog would be it.
"But hey, he was really cool in Adventure 2!" Oh, shut up.
Sonic Generations - Rivals [Sega Blog]