Looks good. Here's my starting few votes:
1. Disgaea: Hour of Darkness
2. Final Fantasy VI
3. Fallout
4. The Elder Scrolls 3: Morrowind
5. Final Fantasy 1
6. Fallout 3
7. Pokemon Mystery Dungeon 2
8. Diablo 2
9. Golden Sun
10. Xenosaga: Episode 1
11. Pokemon Gold/Silver/Crystal
12. Torchlight
13. Persona 3
14. Castlevania: Dawn of Sorrow
For all the M-rated RPGs I've played, I don't own any of them but Fallout 1. :/
But I've played through enough of each game for them to count.
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Golden Sun isn't half-bad, but it needs to cut the crap with the Yes/No questions, which make Zubats look like thylacines in comparison.