[Endoperez]

Betrayal at Krondor had one plot, one "main quest" that advanced the story and might give you access to new areas. But instead of e.g. going straight to Krondor in he first chapter, you could wander around and do sub-quests. When I played it, I didn't get very far in the main plot, but completed many of the sub-quests, and had just awesome equipment for my characters.

In Star Control 2, there was a similar mainplot, but it was advanced more often by discussing with other races and then completing the sub-quests that by simply collecting resources and buying stuff, although buying information could help a lot. But you could go around, to any planet, try and contact all races you wanted, fight sny races you wanted, etc. You could disregard the plot, but of course wouldn't be able to complete it - especially as the plot for once could advance even without player doing anything.

(If you think Diablo is NOT a role-playing game, despite the mechanical similarities, then a game that underlines discussion, strong plot and even rises some moral questions should be dubbed an RPG - even if the mechanics are totally different. But Star Control 2 (anotherSC?!) usn't really the point of this discussion.)

I think that's pretty similar to Oblivion, actually. You have a main quest, which you eventually want to complete, but you can wander around and enjoy the many subquests and the many areas which are optional - at least at this point in the game.