Superstar Class is any skill level from 2000-2999. You can't exceed skill level 2500 in Wii Sports Resort, but in New Wii Sports Resort, you can.
Wii Sports Resort[]
In Wii Sports Resort, the announcer says "Superstar Class!" if your Mii gets to Superstar Class.
In Wii Sports Resort, players face CPUs with higher skill levels than when the player faced them before. A notable example is Ryan, the worst Swordplay player, being near or in the Superstar Class. In New Wii Sports Resort, players face different CPUs that are not seen in Wii Sports Resort.