I don't think there is terrible Mario game though quality in the titles do tend to vary sometimes (Looks at Mario Kart). I'll second the Mario is Missing game, its easy, its short, its hardly educational (Play Where on Earth is Carmen San Diego if you want a real educational game )and its a shame that Luigi gets stuck with being the lead.

Seriously, its like whenever Nintendo makes a game using the Mario franchise that they are not so sure is really good, they make Luigi the main character instead. Poor Luigi...