Any ranking of fanbases is subjective. Personally, I would say the best fanbase will be the Cardinals, followed by the Cubs and then the Red Sox. These three might be hotly contested, and so it would stand to reason that ranking all 30 would be futile. The ranking will change daily based on whatever criteria are used.
The worst fanbase might be an interesting discussion, and the current top choice might be the Tampa Bay Rays.
Catfish Hunter, RIP. Mark Fidrych, RIP. Skip Caray, RIP.
A fanatic is someone who can't change his mind and won't change the subject. -- Winston Churchill.
Experience is the hardest teacher. She gives the test first and the lesson later. -- Dan Quisenberry.