I can't believe I'm going to do this, but I dissagree to an extent. In a way, the movies work well as stand alone films. Infact, each one is quite good on it's own to varying degrees. I mean, Greivous, Syfo Dius, Lord Tyrannus, what do we really want to know? Who really care's who Syfo Dius is? The fact that we don't know adds to the mythology. Greivious was just a pooly executed character, no amount of back story could have fixed what was on screen. Tyrannus, he's just the bad guy, that's all we need to know and he was handled adequately, but not great (in ROTS.)
The problem I have is that when the movies are connected togeather, they fall apart. Concepts are introduced and then contradicted or not consistant in theme, mood or rythum.