I think it was Sonic Adventure I gave up on the series. Robotnik became Eggman (his Japanese name, stupid as it is). Would you take anyone that called themselves "Egg Man" seriously?

I will stick my neck out for Shadow the Hedgehog, though. It gets better with every play through, branching levels (think Guardian Heroes or Outrun), excellent music, great levels... Hands down the best Sonic game in ages. Especially compared to the 2006 Sonic and Unleashed. I haven't played any of the handheld games, but will keep an eye out. I got this big camping trip coming up and a few extra games wouldn't hurt.

Seriously though, Shadow doesn't deserve all the hate it gets.