I think the most interesting thing about Prometheus when compared to Aliens is that James Cameron is also a pretty poor writer, and Aliens only really succeeds on the strength of the plot and the pure adrenaline rush of the film as an action movie, as opposed to one with any real claim to horror or suspense (or, to be more specific, the suspense relies on ACTION as opposed to character, and thus plays to Cameron's directorial strengths).
Prometheus, as discussed at length, suffers from a very poor script but you really see the gulf in quality between the two different styles of film: Cameron never makes films which rely on a great deal of suspense or character, Ridley Scott does and Damon Lindelof lets him down in that regard. Lindelof's script is outpaced by the sheer quality of Scott's director and own approach to character.