All of the above, the great qualities came in many different ways. But I think a common theme was the ability to increase leverage and have a multiplicative effect.

Sometimes this meant being an expert on a certain technology to better leverage it (especially important on teams that need to go deep such as video encoding, CDNs, television hardware, etc). Or looking at needs and pain points across teams and building high level solutions that raised productivity across the board. A willingness to question things and push for better ideas and really seeing them through. This could be at a technical or human level. Some people were really good at improving team cohesion and empathy, causing teammates to work more effectively. Others pushed hard for internal education and sharing learnings to help raise everyone's game. The culture of the company helped enable all of this. Some people excelled at improving culture, which has a leveraging effect as well.

I have seen the above at just about every company I've worked at. But I would say that at Netflix people took it further and were more successful than I've seen elsewhere.

That's just my experience, I've only worked at a handful of companies. I have no doubt many companies have employees that do all of this.

The question would be what other companies did you work for? If it's all top tech companies in the valley, it should be pretty good across the board.

You're right. I've not worked at all top companies, but I would still say the lesser known ones had good employees for the most part.