They simply took the Van Buuren design documents and made a game based on them. If you have such a good team (Obsidian) + semi-canonic source, then it's hard to make a bad game. Honestly, NV is good game (where it fits canon), but I don't like any of the DLC's we have so far. Don't know about of the upcoming Old World Blues (what we know atm sounds promising) and Lonesome Road, so we shall see what they will come out with.