Didn't we already cover this discussion on dark side transitions before it was deleted by RedHawke? The dark side of the Force does not change your physical appearance directly. Your actions, caused by the dark side's influence, do. Palpatine (Darth Sidious) was completely normal until he zapped himself with his own Force lightning trying to kill Mace Windu who wisely used his lightsaber to deflect the energy. Darth Vader was so similar in appearance to the "deceased" Anakin Skywalker (read the novel) that everyone, including the Jedi at the Temple, thought they were talking to a misled Anakin. We all know how his body changed form. Obi-wan severs his remaining limbs and then Vader is burned alive by being too close to the lava. Darth Maul apparently always had his tattoos according to GL, and Count Dooku (Darth Tyranus) never even gained Sith eyes, but because of his shear mastery of the Force in general. (A former Jedi master, personally trained by Yoda, secretly learned Sith Lore after achieving master, and leaving the order after his former Padwan's death [Qui-Gon Jinn]. Yes, Obi-wan and Anakin are like his grandchildren, and he even admits this in the ROTS novel) He became a full-fledged Sith apprentice who even had plans to properly dispose of his master Sidious. He tried to recruit his elder "grandson" for this task, but Obi-wan was too well trained as a Jedi to become a Sith apprentice.
Count Dooku, aka Darth Tyranus, looked exactly the way he did when he left the Jedi Order. They never even gave him sith eyes, yet we know from the Clone Wars TV series produced by GL that he was very much a Sith Lord through, and through.
Oh, and despite what you guys might think, Luke Skywalker does briefly turn to the dark side at the climax scene in Return of the Jedi. It wasn't until after Sidious offered him apprenticeship, officially, that he changed his mind. But, up until that point he was headed down that path ever since his Step-parents were ruthlessly murdered by Imperial Sandtroopers at the order of Darth Vader. (Read the novel) He wanted to become a Jedi to avenge his family's death. Not to protect innocents. Everyone knew he was a step away from the dark side, even Luke. (That was why he wore black as a reminder.) It didn't help when Sidious turned his slipping into a fall, though, if you get my metaphorical meaning.
So I ask you, fellow Lucasforum members, why do we prefer the comic book style dark side transitions over the movie style ones? My answer is because we like to see that a person is evil. It makes it easier to kill a person that looks ugly and deformed than to realize that his actions alone make him evil. Do you agree with my logic? Or do you think I am completely insane?