Not the worst movie ever
I don't know why so many people hate Shanghai Surprise, because I've seen movies that are far worse, and far more boring than this. I actually thought Madonna gave a decent performence. Yes, I'm a fan of hers, but I actually hate most of her films (the only ones I like are Dick Tracy, Desperately Seeking Susan, A League of Their Own, Who's That Girl, and to an extent Shanghai Surprise...the rest are dire).
But really, this movie is slated far too much. I think the main reason people hate it is because it's Madonna, and because of the fact that she and her then-husband were the stars. If it had starred anyone else other than Madonna and Sean, I don't think it would've been as badly receieved as it has been.