He does become good by his/her (or rather your) own choice. The Council didn't have a mind control thing over him. If they did, you would be forced to stay LS, and despite the fact I probably ever once went DS, I would be pretty peeved if I didnt have the choice.
I knew you were going to say this. Well still it doesn't make Revan a good Jedi.
All his victims care not, if he killed Malak or not. He will be always a slayer and murderer of millions , while Luke not. Luke is a perfect Jedi who stood against impossible odds. He doesn't have to redeem himself cause he is pure all the time.
The only reason that you defend Revan is, that he makes you feel that you're really special superman.
What do you know! I thought you were going to bash me for that as well! Thanks pal! :cool: