Hmmm this is like asking who is better, your doctor or your mechanic. They both have distinct skill sets. You have to be more specific. What criteria are we judging by? Medals, appearances in the final event? Number of Olympic games?

Is it safe to say Phelps is the best swimmer of all time. Yep. Not only by Olympic standards, look at the past 5 or 6 years. The guy is dominating. Truly amazing.