My least favortie "A list" directors are:
Joel Schumacher
Michael Bay
Brett Ratner (Rush Hour 1 and 2, Family Man, After the Sunset, Red Dragon) - a master schmoozer, he himself admits it's his phenomenal ability to make friends, not his talent, that got him where he is today. The Rush Hours were good, but that's because of Chris Tucker.
Stephen Sommers (Mummy films, Van Helsing)
Kevin Smith - though his screenplays are comic masterpieces.
Roland Emmerich (Independence Day, Day After Tomorrow)
And, in the "were once good, but now suck" category:
George Lucas
John Singleton
The Hughes Brothers
Francis Ford Coppola '
Ron Howard (sometimes) - Beautiful Mind and Apollo 13 were brilliant, The Grinch and Ransom sucked. Very hit or miss director.