1. Super Mario Bros.
Called the greatest game of all time by IGN in 2005, this 1985 release by Nintendo defined the side-scrolling genre. It has inspired several sequels and spin-offs, and has recently celebrated its 25th birthday. It's simple, pixelated, and iconic.
Why it would make a terrible film: It already is. This may be cheating, but Super Mario Bros. has already been bastardized by the big screen. Nothing in the movie has to do with the game except that Mario and Luigi are brother and plumbers and that Daisy and various villains are involved. There's no bright shiny world with troublesome turtles and kind-hearted mushroom people; the setting and costumes are full of bad 80's references, dinosaurs have apparently evolved in a parallel world to look human, and not only is the princess not in another castle, but the romantic storyline follows Luigi and Daisy - Mario already has a lady, and her name isn't Peach or Toadstool. This movie should be a warning to all potential games ever considered for film - writers and producers will change and play with the game's plot to try to make it relevant to viewers rather than use what they have. Plot integrity means nothing next to perceived revenue, and abominations like this 1993 movie that even star actor Bob Hoskins regret, will be the end result.