While Bioware games has some linearity, I still wouldn't kill them totally linear. We're a far shot from Final Fantasy here.
You can decided which part of the world to visit first, which quest to complete or not and how you will complete them (which often has an impact on the rest of the world) and even when it comes to companion npcs, your decision can end up leaving them out of your party altogether (Leaving Sven in his cage or Grunt in his pod are fairly common occurence from what I gathered) or cause their death.
Bioware games really make me think of a good old pen and paper game - yeah, you can do whatever you want (to a degree), but ultimately you are going to go through the Game Master's story.
Steve Fidler said:
It is a very difficult thing for a well known developer to accomplish because it often results in long development time. These companies are more interested in producing a game from their primary franchises every year than producing a quality game. Bioware is well known for their non-linear gameplay, best portrayed in games like Baldur's Gate, Neverwinter Nights, and Star Wars: Knights of the Old Republic.
I'm not sure how KoToR fits in your idea of non-linearity, since it basically laid the groundwork for the Bioware 'Intro > 3 Planets > Ending' recipe.
It's been way to long since I played BG and NWN... all I really remember from those games is that they were great... but unless I'm mistaken, at some point, you HAD to go in some places to have some keys event happen in order for the story to progress.
If nothing else, Baldur's Gate gave more of an illusion of freedom because of the map (which was really similar to the one in DA, but with a bit more freedom in where you could move)... but really, replace the map by Space and turn the 'hubs where something happened' and you pretty much have the ME map...