@C-Bear: I never did play Fallout 1 & 2

so I really can't comment about those. I'd argue, though, that given a campaign that you play through in PnP RPGs, a second and third playthrough would give you pretty similar results in terms of the main plot points and ending as the first playthrough. There is a reason D&D drew on dungeons so much. Besides the obvious fun factor and scare factor and a natural habitat for monsters and traps, it's a setting where there is less obvious way to go off script and ruin a DM's day. Our DM always got out party inside a dungeon in the first 5 minutes of play so that we didn't screw him into having to think up a whole new story on the spot!

This is dealt with in most cRPGs by being forced to limit the players interaction with the world; there's no DM you can describe your actions to. However, once you've done what the game allows you to do in it's interface, it's got the same rule set that a DM is equipped with, save for creativity. (Except I remember in NWN, they tried to implement a DM system, where a DM could run an in game campaign with his party with a VOIP system. Horribly implemented, way ahead of its time.)
I do agree 100% with your assessment regarding the genres!