You should see Sonic X in its orginal japanese with english subtitles, and if you dont like the first and second season then atleast try watching the third season. The third season in its orginal uncensored japanese is VERY dark for being a Sonic.
Dark Super Sonic is pretty darn awesome. However, I always thought he'd be weaker, due to the fact that it was apparently a result of the impurities inside the Synthetic Metarex Chaos Emeralds, and only lasts as long as Sonic's rage last apparently, as well as he isn't as impervious to harm as his regular Super Form is. Almost as strong as regular Super Sonic, but not completely.