How can you say no Sonic game has good dialogue without mentioning Sonic Adventure 2?
With classics such as
"So you're not just an ordinary hedgehog after all."
"I just don't know anymore; what my purpose is for being here..."
"For all the people on this planet...I promise you....REVENGE!"
"Our threats fell on deaf ears."
"Impossible...I am the ultimate life..."
"Even if I am a fake...it's still me...Shadow...and I will fulfill my promise to Maria, that's the only thing that matters to me now."