The film, which many critics hailed as a reawakening for the zombie genre, came out in late 2003. Assuming the game went from concept to development in a year, it would have released in late 2004. Resident Evil 4, also known as a reawakening for the zombie genre (or, at least, a rebirth of the then-falter RE series), would arrive in early January of 2005. A 28 Days Later game would have likely been ignored at the time, or looked down upon for its relation to box office and over-saturation of a popular gaming genre (horror). Some things are better left unlicensed.
According to Box Office Mojo, 28 Days Later earned over $82 million worldwide -- not bad for a film with only an $8 million budget. Screenwriter Alex Garland was reportedly paid $1 million for writing the Halo script because of Bungie's admiration for the zombie film.