I know that this topic is quite general. I always get different answers though. People defend the game they play as the most difficult. The set of rules you play under also need to be factored in. Shot making skills vs position play also might alter your viewpoint. I generally rank the games based on what games I have played in my lifetime. I was born in 1948 and started playing around 1955. I rank the games from those requring more skill to less as follows:
Straight pool
One Pocket
Nine ball
Rotation
Eight ball
I have played other games such as cut throat, snooker, bank pool so seldom (or in the case of seven ball and ten ball... not at all) that I could not rate them with any knowledge but they all should be considered. What annoys me are the bar room eight ball guys who think that their game is the best and look at you like you are from Mars if you make a statement relegating their game to the depths where it belongs.
Straight pool
One Pocket
Nine ball
Rotation
Eight ball
I have played other games such as cut throat, snooker, bank pool so seldom (or in the case of seven ball and ten ball... not at all) that I could not rate them with any knowledge but they all should be considered. What annoys me are the bar room eight ball guys who think that their game is the best and look at you like you are from Mars if you make a statement relegating their game to the depths where it belongs.