I, personally, find 8 Ball more challenging than 9 Ball. To the previous poster who stated that a good stroke was not required in 8 Ball...I call bollocks to that! A poor stroke in 8 Ball will cost you the game, and quickly. A poor stroke in any of the games will cost you...it is the single most essential aspect of the game, IMHO.
9 Ball became popular in pool (for road players) for exactly the same reason that Texas Hold 'Em became popular in poker...both games are typically played in a short time frame, which allows for more money to be made in a shorter amount of time. When the road players started to play on the tournament circuit, they brought the game with them...which is why it overtook 14.1 and 1 Pocket in popularity.
8 Ball became popular with the 'everyman' because the basic rules and concept of the game was/is easy to understand from basements to poolhalls. When you start to apply BCA rules to the game, and begin to see the intricacies and strategies...the 'dance' as it were...is when the game takes on a whole different face.
Lisa