Another thing you could focus upon is the difference between the journey of the characters in each novel. In The Hunger Games, Katniss is alone (essentially); whereas, in The Road, a father an son take their journey together. You may choose to analyze the differences seen between the choices and paths taken by the protagonists.

I think the most important thing you need to decide is the organization of the essay--what aspects of the two works can you most easily compare?  Both works feature post-apocalyptic settings, and both incorporate violence into the storyline.  It would be interesting to compare the futuristic and dystopian elements of The Hunger Games against the post-apocalyptic setting and devices in The Road.