Yes, RQ 3. I have not played RQ 2, so I don't know the rules of it. The differences to RQ 3 are:
- No general HP, only hit locations.
- No fatigue point system (and therefore the spells and monsters relying on them are gone), but a replacement with fatigue levels.
- Common magic is pretty much the old Combat magic. Effectivity of Sorcery and Divine magic are now defined by the casting skill level of the user, not his free INT or POW. All spells a divine caster now knows have the same strength (skill divided by 10, rounded up...someone with 4 divine spells and skill 55 casts them all at intensity 6), and the 2:1 advantage from RQ 3 is gone.
- You don't sacrifice POW or stats for enchanting stuff or gaining divine magic. For enchanting you use permanent MP now, and for divine magic you reserve a pool of POW (so you have less MP) to determine the number of spells you can learn.
- You don't measure magic attacks MP vs MP any more, but against the skills Persistence, Resilience and Evade.
- Combat is totally different, because each character has a number of combat actions (determined by INT and DEX, the higher the more actions), which can be used to attack and defend, instead of attack/defense.
- Weapons have reach and size, which define who can parry what and attack distance.
That are the things I can think offhand. The monster statistics don't look much different, except they have no fatigue anymore, and combat actions, reach and weapon size have been added.