I personally thought that Fable was a bit weak, I played number 2 but it was something of a chore to get through another of Peter Molyneux's games which was preceded by lots of big talk but failed to deliver as much as was promised - but at least he aims high...
Red Dead Redemption on the other hand, was excellent once it got going.
For RPGs - have you tried Fallout 3, Mass Effect 2, or either of the Dragon Age titles?
The games that you mentioned you liked seem to suggest a big open playground for you to explore - Assassin's Creed: Brotherhood (or Assassin's Creed 2) are both excellent, but may be a bit too 'platform' for you (there's a fair bit of running and jumping involved in assassination, as well as Stealth and problem solving)
Grand Theft Auto would also fit in this, but I've not been such a fan of the recent title; very pretty but lots of niggling faults, and (in my opinion) not as good as RDR. Just Cause 2 is quite good fun, big open playground lots of explosions, huge maps, plenty of vehicles to obtain - iffy voice-acting and can get a bit repetitive, but still good for a play through. Alternatively, Crackdown is fairly good fun, but doesn't feature any puzzles.
Don't forget that Portal 2 is out soon, and if you've not played Portal it would be an ideal time to try it.
Any of those appeal?