...would we still have had Sonic Heroes? This was a question I asked at the Sonic Stadium. I think its an interesting question, just as "In Back to the Future, what would happen had Marty knocked up his own mother?" Food for thought.
I received some interesting replies. Some thought that Heroes would have come out on Dreamcast (exclusively, of course) and the rest of the games we have now would have followed suit. As Sonic Riders Zero Gravity would have been the last Sonic game to appear on the Dreamcast, and we would have been treated to a much better Sonic '06 as a launch game for the Dreamcast 2 or Sega Cyclone or Sega Infinity (basically Sega's next step after the Dreamcast).
Others believed that we would have been treated to a Sonic Adventure 3 with a plot similar to Sonic Heroes and gameplay that was more in line with Sonic Adventure 2. This led to a bit of complaining over how some Sonic fans believe that Sonic Adventure 3 is just a fanboys answer to the perfect Sonic game that never happened. Those who think a third entry in the Adventure series would have saved us from "the dark times" are complete loons who are better off wishing Sonic & Mario would team up (wait, nevermind that last part).
This discussion inspired me to design boxart for Dreamcast games that might have been, had the console and Sonic series lived on together. Enjoy!