The plot's too familiar
Not bad with the sprites. You deffinately know how to use them well. Your story idea isn't bad, but it's too much related to the Sonic Battle game. I mean, sure, it's your own ideas for the fact this robot is going to be the "ultimate weapon," and that it doesn't want to live for its purpose as much, but that's sorta how Sonic Battle goes: a 5,000 year old robot, known as "Emerl" from Sonic & pals, whom was originally built to destroy by obtaining all the Chaos Emeralds (which Emerl craves for) decides to live differently. Like I said, good story idea, just too much close to Sonic Battle (at least, what this trailer has taught us).