i think it caught on because of it's opening price point, the novelty of motion control and it came with a game which utilized the new controller very well. also, as everyone mentioned, there are several quality games for the wii.
(nephew = boy and niece = girl)
your nephew or niece is of a completely different age group than you are so i don't know why you are surprised that that person is enjoying a console that you do not. as young as we all want to think we are (i'm 33), we can't always relate to what someone else feeling. don't prowl the internet trying to recapture your youth... it's not really a young girl.
personally, i don't like ultra-realistic games like you do (gta4, cod, re4?) but i can accept that your taste in games are different than mine.
EDIT: i also don't mean to insinuate that only young people like the wii... it just depends on what people are looking for to enjoy themselves.
