Egoraptor of Awesome Series (such as Metal Gear Awesome) fame is doing this series of videos where he talks about games and their sequels, and it’s really interesting. There’s only two eps so far, one on Castlevania and one on Mega Man and Mega Man X.
The Mega Man one in particular is a good watch. MMX is one of my favorite games ever, but I didn’t realize how much depth it really had.