Funnily enough I never had much of problem with his writing. It's not any worse than your average video game writing and he has plenty of good ideas and knows how to keep the player interested, even though I do admit that Fahrenheit and Beyond kinda fall apart at some point.
Average videogames usually do more things than just telling a story.
David Cage games are basically only story and nothing else, thats why the quality of the writing is kinda tenthousand times more important.