Right. In SA2 he was a dark and mysterious fellow that was quiet about his traumatic past and sided with the enemy in an attempt to further his own goals, when in Shadow the Hedgehog he just continously whines about his problems and seems a lot more broken than bad. But of course, you could pull the "Shadow the Hedgehog isn't canon" card.
Also, Sonic the Hedgehog isn't the series you want to look forward to for character personality. That's sort of what spawned Sonic the Hedgehog 360/PS3. Not gonna pick a randomly developed Mario character over the classic plumber, right?