Depends on your definition of a good or great fan.
I remember reading several months ago (towards the end of leg 2 or beginning of leg 3 I think) that concert goers in the US spent much more per concert attendeee on merch at the shows than any other country or region. Concert merch sales are generally considered very high profit.
The crowds might not be as wild as some other places (personally I don't find wild and crazy crowds all that appealing), but money speaks volumes, so by that measure the US fans could be considered the best. Of course fans in other countries may very well spend a much larger percentage of their income on concert tickets and merch etc., so they may well be considered better fans (from the strictly financial point of view).