Not to mention that you realise the book that opens at the start of BG2 and the expansion will eventually become your bible of sorts, detailing your journey, YOUR experiences and results in your followers to be of your alignment and as they describe it "your name shall be a beacon of hope in times of darkness, tales of your life shall inspire and guide while servants of evil flee your wrath" (good ending). Most importantly, YOU have the choice to throw that away and remain who you are, with your companions actually giving you advice on what they would do, you romance options are of dynamic characters who actually may make you reconsider your choice.
Also, redeeming Saverok and developing Imoen to be a woman of confidence from the shy thief you fled Candlekeep with to the powerful Archmage, apprentice to Elminster and establishing her own thieves guild. That is the power choice and good characters can give you in an RPG.
Not to mention the music kicked ass
