[Note: Written as someone who really liked the original series, but merely watched the prequels.]
So you can largely look at the prequels (Episodes 1-3) as "The Downfall of Anikan". Going into the movies you knew the outcome (Anikan was going to be a Jedi, only to be turned to the dark side). They had three movies to show this.
The problem? The real turn seems to happen somewhere between the end of episode 2 and the beginning of episode 3, and it really is not that believable. So you have three movies to show me the downfall of a man, and you choose to largely have that turn happen in the time between two movies?