I disagree with the overall message of this article. Comic book movies and TV shows have been around for years, and they are finally starting to turn out well. Why would superhero movies be on the decline now of all times, right when The Dark Knight shatters records at the box office. If anything, this will encourage studios and producers to make
more comic book movies. Not only this, but Marvel has already laid out plans for Thor, Cpt. America, and Avengers movies. Sure some of the big ones of have been done, but this is only the beginning.
Not only this, but please name a movie based on a video game that was actually a success both commercially and critically. Both of the movies you named (Doom and Hitman) were not good movies. At all. There has been a slew of video game movies (Tomb Raider, BloodRayne, Resident Evil etc.) and none of them can really be considered good movies. Entertaining maybe, but none of them have been successful enough to spur producers towards an actual video game movie spree.
Long story short: Comic book movies are not done, they have about another decade. Video game movies also have about a decade until they actually are on the same level as real movies.