To be honest, I think Greenlight is one of the worst things for Steam. You are basically judging an idea, with no real evidence and have to trust the dev to make something good. It’s not as bad as Kickstarter where you have to pay upfront, but it blurs the Steam-Market. There are good games which made it on Steam through Greenlight, but it’s still a flawed concept. Some kind of quality control before the release would be great, even if that means that the games get delayed.
While the rating system works in many cases, there are some problems. As far as I know, I’m not sure if that got changed or not, devs were able to moderate the ratings. there are a lot of joke “ratings”, which are not even funny in many cases or have been repeated a hundred times.
Valves attempt to open up Steam allows many indies to get their games easier on Steam, while that’s a good thing in the first place, it also allows bad people to put stuff on there. Even worse, there is no way for the users to report a game for bad quality. You can flag a lot of things, but poor quality is not in the selection, why? People should start to care about quality a lot more, this would prevent many of those garbage games to be released.