The Stanley Parable/WMG

1/3 - The Golden Ending is actually a good ending.
Because the narrator only acts as such. He's not Stanley's boss. He's the narrator. His aren't orders, they're more like hints. The story he wants to tell is that of Stanley's escape. Of course, Stanley has to cooperate, and the five bad endings are the result of Stan not doing so. The narrator is more like "trust me, only I know the way out" rather than "obey and you'll be free". Of course, the Fridge Horror of "without anyone to tell him how to feel, he was happy" remains (the sentence implies Stanley suffered for his entire life, faking his supposed happiness), but still, he has an opportunity to make his own, new life. Even if his past existence makes him unable to relate with other human beings at first, as soon as somebody notices it, he or she will help Stan with his issues eventually, and maybe his boss will get what he deserves. And this leads us to the next WMG...

2/3 - The bad endings aren't canon because...
... those were actually the fate suffered by everyone else in the building. The only one who escaped that fate was the one who deserved it the least: Stanley's boss. Therefore, the narrator is...

3/3 - The narrator is Stanley's own mind.
Freeman's Mind jokes aside, well, yeah, it is. Because all the past years of Stan monitoring the other employees, their mistakes (see the previous "2/3" WMG) developed in Stan a strong common sense, eventually evolving into a voice in his head - the narrator. Said narrator told Stanley what to do in order to avoid the same mistakes made by the others, which is why the narrator calls Stan out on disobeying his instructions. Of course, playthroughs in which players go Off the Rails may be either be interpreted as a Violation of Common Sense or as Stanley simply forgetting what he learned by watching his former colleagues. Similarly, the narrator getting more and more upset (as well as the "room without textures", and everything that ensues) is a metaphor for Stanley going crazy due to his escape not going as planned.