5. Halo
For many a video game fan, this is a particularly sore entry on this list, given the farcical quality of most video game adaptations. With the 2005 announcement that Peter Jackson would be Executive Producer - but sadly, not director - on a Halo film, fanboys rapturously responded that finally we might get a worthy take on one of the decade's most popular gaming series. Jackson appointed the then-unknown Neil Blomkamp as director, a bold choice that would later prove smart had the film ever gone into production, what with Halo's failure causing him to direct the fantastic District 9 instead. After a stilted production and three years of flitting about, Halo was cancelled. The depressing reality is that this failure will likely tarnish Halo for the considerable future, such that we shan't be expecting an adaptation any time soon. And even if it happens, are they going to be able to rope in talent as assured and skilled as Jackson and Blomkamp?