My list…
1. Baldur's Gate 2
2. Baldur's Gate & TotSC
3. Dragon Age: Origins
4. Mass Effect 2
5. KotoR
6. Mass Effect
7. NWN: Hordes Of The Underdark
8. NWN: Shadows Of Unrentide
9. Jade Empire
10. NWN OC
For the record I hated Jade Empire's action gameplay mechanics and basic leveling/skills system so I'd say NWN OC beats it there. However, JE at least tried a new setting, had some great music and nice graphics which I'd gladly take over NWN's general blandness, so it is above NWN on my list.
I bought Throne Of Bhall 2 years ago and I still haven't played it yet. Soon. Have not played DA 2 yet.
Also, not sure about Mass Effect's place on my list. I loved the beginning and the end but the middle of the game bogged down too much for me and the Mako was just unforgiveable. However, I haven't played the other games below it on my list in a long time.
Now, if we add the Obsidian sequels on here, my list would look like this:
1. Baldur's Gate 2
2. Baldur's Gate & TotSC
3. Dragon Age: Origins
4. Mass Effect 2
5. KoToR 2
6. KotOR
7. NWN 2: Mask Of The Betrayer
8. Mass Effect
9. NWN: Hordes Of The Underdark
10. NWN 2: OC
11. NWN: Shadows Of Unrentide
12. Jade Empire
13. NWN OC
Of course, I'd have to replay some of these to really be sure about these rankings
The only thing that will never change is BG2 & BG1 at 1st & 2nd place and NWN OC at last place!