To me, there seems to be schools when making a game.
One is Bethesda's school in which you're the character that does all these things. You need to use your imagination pretending to sneak, steal, or kill someone, be it guards or monsters.
I don't know when developers did promise virtual worlds?? I mean, it's not like we've been promised something like the Holodeck in Star Trek, is it??
The other, is of course, the school of Bioware in which the developers are dedicated to telling the greatest story ever told - every time. To do this, the game needs to have a beginning, a middle and an ending, following the narrative path for the western culture that Aristotle set down may moons and sun ago in ancient Greece. You then play as that character, not as yourself; it is your character, not you, that does kill monsters and people.
If I were to theorize a bit, I would say that Bethesda's approach was more like 'playing' and that Bioware's approach were more like 'gaming'. In 'playing' there are no rules, there are only big open worlds for you to explore, 'gaming', otoh, has (some) rules you must obey - or else you can't play (or game...)
Bethesda seem to keen on making real worlds life simulataors i.e. creating a believable virtual world (something they failed abit with doing in Oblivion, imo) while Bioware seem making great stories that has very good dialogue (options).
Imo, Fallout 3 and Dragon Age could mean a sort of mix of these two schools...
That is not necessarily a bad thing...