I definately agree. 4 reasons why :
1. It's the best Brat Pack movie in terms of quality. The script, performances and concept are all absolutely superb. It's the one whic has had the biggest influence on pop-culture too.
2. It's directed by John Hughes, the quintessential Brat Pack director.
3. 16 Candles and Pretty In Pink are, basically, chick-flicks while Weird Science and Ferris Bueller are guy-movies,right? The Breakfast Club, however, is a movie that both girls AND guys can love.
4. Ringwald, Sheedy, Estevez (apparently he was the unofficial Brat Pack leader), Nelson, Hall - no other Brat Pack movie contains such a strong cast.
You could argue that St Elmo's Fire contains an even stronger cast since it includes 4 of the above 5 and other top-tier Brat Packers like Rob Lowe and Andrew McCarthy alongside a third-tier Brat Packer like Demi Moore but i'd argue that, as good as it is, it isn't anywhere near as good as The Breakfast Club, and thee definitive Brat Pack movie should be set in high school not college like St Elmo's Fire was and has to be directed and/or written by John Hughes like The Breakfast Club was and St. Elmo's Fire wasn't.