6. Laufey (Thor)
First things first; I know Laufey's dead, after Loki (his biological son) killed him in the first Thor movie in an attempt to prove his worth as King of Asgard to his adopted father Odin. However, death means very little in the world of superheroes and villains, so he could always come back - or he could appear in a prequel/flashbacks. Essentially, it would just be great to see more of Laufey, the Frost Giants and Jotunheim, as some of the best scenes in the first Thor movie took place in the icey, atmospheric realm which Laufey ruled. More footage of the great war between Asgard and Jotunheim would suffice - or indeed a look in to Loki's birth and sequence of events that led to him being abandoned by his Frost Giant father - however, a full prequel movie which focuses on the history that Asgard and Jotunheim have would be absolutely fantastic.