Depends on the game. In Twisted, I'm glad if I'd make it past 40. In Gold on the other hand, I have scored 110 points in Mona's story. That's the highest I have ever scored in any WarioWare game. In WW:MM I used to score 80 in Dribble and Spitz' stage.
Depends on the game, story and microgame. For some of the harder ones, anything above about 30 is probably impressive, especially some boss microgames and certain finicky/microphone based ones. For trivial ones, a score of 300 or so would be impressive. It depends.