Sorry for the long post in advance.
Apocalypse is currently listed as a member of the four horseman. I would like to throw out there to remove his status as a horseman. I understand that he is the leader of the horseman, but I don't think that he qualifies as one of them. I cannot think of anywhere in the comics he has ever been cited as being one of them, or said anything indicating that he considers himself to be one of them. Most importantly, I don't think he would consider himself one of them. They are more his lackeys (or followers), doing his bidding and following his orders than anything else.
I would liken this to Magneto and the Acolytes. I would consider Magneto the leader of the Acolytes, but I don't think he would be counted as one of them for similar reasons.
Two examples that I would see as contrary to this would be Professor X who has been the leader of the X-men before and could also be considered one of them or Magneto being both the leader and an active member of the brotherhood of evil mutants.
I don't know if it is worth opening up multiple threads for, but I think that Apocalypse should be removed from the four horseman as well as magneto being taken out of the acolytes.
What do you think?