Mario Party's first week sold 28k in EMEAA. I don't know why anyone expected Wii Party to sell enormous numbers with this data.
That being said, Mario Party sold 32k in the 20th week of sale and over 2 million total in EMEAA, so Wii Party could sell a moderate amount for a very long time.
Anyone can guess. It takes no effort to throw out lots of predictions and have some of them be correct. You are not and wiser or better for having your guesses be right. Even a blind man can hit the bullseye.