Not really, thats a bad comparison. IF anything Harry's set up to be a Goblin is the equivilant to the Joker card...and got just that; Harry became villain. Connor's role in the 2nd was a cameo Easter egg at most. Nothing in the movie set up anything for him to be a villain down the line. Now his role in SM3 is a different subject. They actually expanded his role to a supporting a character and involved him in the main story. His lizard stuff in the background plus studying the symbiote could very possibly spark an interest in him to develop the Lizard serum.
Yea they totally forgot about him

...hence why he wasn't in the movie at all....oh wait....