Sega seems to be on the right track with the concept and development of Sonic Generations, reaching back to all of the great games in the early days of the franchise to use as source material. The game isn’t going to be all “old” stuff though; the modern era Sonic the Hedgehog is getting some acknowledgment too as shown in the new trailer above.
Crisis City, Rooftop Run, and Planet Whisp are all getting the modernization treatment. Just because the games that featured these stages originally were pretty bad, it doesn’t mean that the stages themselves were. It will be interesting to see how they fit in when used in a “better” game.