The only "fake" one is Madonna's, but it was for a video and it served a purpose. Britney was crying because she felt like she was being suffocated by the media. Avril's was from her Wish You Were Here video which is a really touching song. Adele is crying because she won Album of the Year, the same as Gaga would do. There's no need to shade people's emotion.
The only fake cries are Avril's and Madonna's, and I think that Gaga's and Adele's were for excitement, and britney's were because she was passing a bad time in her life and she was feeling like trapped