The closest thing to a good thieving system I have seen has been in a NWN PW with permadeath and PvP. Sure, you could pickpocket, break into houses, and backstab people for their gear. But in a permadeath world, you were ultra careful about what you targeted, and rogues aren't exactly buff fighters in D&D.
One time I chanced upon a Drow in the woods. He was hunting a bear, and asked for my help. I was a bit creeped out, because we all know that drow are evil. But I said ok since I figured he'd stab me if I didn't help. He went up to the bear and started attacking (which was terrible tactically.) He got mauled pretty bad and was knocked to the ground bleeding. I set a trap and let the bear come to me, killing him. Then I went up to the drow, finished him off, and looted the body. That was good thieving.