One of the more unique aspects of the American Horror Story series is there use of the same actor/actress playing different characters in each of the seasons. For example, Jessica Lange played Constance Langdon in season 1, Sister Jude Martin in season 2, and Fiona Goode is season 3. This also goes for the other four actors who play different characters in each season (Evan Peters, Sarah Paulson, Lily Rabe, and France Conroy). Since I have seen very little of the American Horror story series, it is hard to critique the effectiveness of this aspect of the show, however, I feel that using the same actors each season has more cons then pros.
First the pros. People who watch the series that have a liking towards a specific actor are more likely to remain watching each season because they enjoy that actor. Also there is much exposure to different acting skills within each actor due to the switching of character roles. I believe this is someone effective towards a dedicated audience and that's it.
There are many cons to this aspect of American horror story, in my opinion. The main one is that the audience may become attuned to a certain emotion or aspect of a character, and when switching roles the next season, I believe this can cause some sort of confusion in the viewers mind. The first season, Evan Peters was a ghost who kills people, however in Season 2, Evan Peters played a gas station attendant with a wife, he is also "kind, loving, and mild-mannered, avoiding confrontation..." (american horrorstory.wikia.com). So the person who watched season one is attuned to Evan Walkers being a killed, but now is season 2, he is a loving man with a family. This seems a little confusing, and this is the same with the other characters in the series. I am no saying that this is a bad thing, it does add a unique element to the series in terms of mysteries, with wondering who is going to play what next season.
-Tyler Tillinghast