I enjoy the Nationals and usually make the trek out to Southwick and Unadilla most years --though it has been less consistent the past few. When I lived on the West coast usually made to at least one outdoor event every year. Some places were better than others.
These days it is often hard to get even rider buddies to go most years to outdoors events. The outdoors version of the sport is just not that great for spectators. My buddies that ride --except for one who posts here on TT-- don't even keep up with the outdoors standings anymore.
SX is really keeping the sport alive I think and main circus that younger folks are enjoying most is the Nitro Circus... Maybe it is different in Europe.