Give a stream of consciousness and then the final answer. Several novelizations of each of the six films and some comic books as well as original canonical novels based on the franchise have been released. The original novels include Alien: Out of the Shadows, Alien: Sea of Sorrows, Alien: River of Pain, marketed as the Canonical Alien Trilogy and the short story collection Aliens: Bug Hunt. Out of the Shadows and River of Pain were adapted into audio dramas in 2016 & 2017 respectively released on the Alien Day of the respective year. Alan Dean Foster published Alien: Covenant -- Origins, a novel set between the events of Prometheus and Alien: Covenant

Based on this passage, how many movies are in the aliens series?
To answer the question, consider the following: Several novelizations of each of the six films and some comic books as well as original canonical novels based on the franchise have been released.
So, the final answer is six.