Viagra was introduced in 1996 and was an immediate hit among aging Romeos. High-profile spokesmen like Bob Dole and Dick Butkus helped produce sales exceeding $1 billion in 2000. The drug worked in about 75% of men, but it was expensive and required careful planning (and wishful thinking) because its effects lasted only a few hours.
Cialis and Levitra were the next generation of ED-fighting drugs. Cialis was called "the weekender" b/c it worked for about 36 hours.
However, many men got better effects from Viagra.
Australian researchers, in a review of literature, concluded that Cialis works best for most men but said that the only way to tell in an individual case is to try each drug for a short time and see which one the patient liked best. (International Journal of Impotence Research, 19: 282-295, 2007