he most crucial part of my game in mind is the cut scenes.
Somehow, I think that a great game needs a great mechanics + nice some nice audio/visuals can help (But, as "Thomas was alone" (non-C2 game) shows, you can make an incredible game with just grayscale boxes ;-) )
I'm not sure if great cutscenes alone can make a great game, but I wish you success, and I hope to see one :-)
Anyway, have a look at "Arcade" - there are quite a number of games with downloadable source.
You can also take a look e.g. at gamedevelopment.tutsplus.com for more C2 tutorials.