I think this is an interesting question because you can look at it two ways: games that feature the same worlds and rules as tabletop RPGs, which are relatively easy to find, and games that offer the same sense of possibility that tabletop RPGs - at their best - have, which are much rarer.

You hint that you're looking more for the first category, so I can suggest plenty of games like Baldur's Gate and the like, but it might be worth giving some thought to the second.