After Obi-Wan killed Darth Maul, Yoda granted him the rank of Jedi Knight because he was the first Jedi in 1,000 years to kill a Sith. Later he became a Jedi Master. Having said that, the game isn't just like the movies. Assassins can use Force Lightning but you never saw Maul use that, etc. Some of the movie characters are two classes combined, so Obi-Wan really is like a Consular and Knight rolled into one.