Meh, it depends on the context.
Valve could definetly rework the Review and rating system and make it a tad more convenient. When you hit up a Game on the store, it should be easily visible how many people bought the game, and then how many of those people were satisfied and how many werent. The current "Recommendations" at the bottom are a step forward, and i've dodged a few bullets by reading them. Still, its a bit annoying that this is the only more or less reliable source of feedback. Granted, you can see the Metacritic score on the store page, but it lists only the one from the Reviewers, should list both imho.
Abbout outright broken games. There should be a refund or return policy for games who are proveably broken or dont function. (Talking about crashes, the lack of _promised_ features, you know the deal.)
However, on _QUALITY_. I seriously dont want a third party deciding if something gets released on steam or not, simply based on "rating". Someone mentioned Dwarf Fortress, which is a prime example. I've seen people dismissing it for a broken, bad looking mess, unworthy of being called a Game. This is why user ratings and some research is so important. I dont want the Store to sort out stuff that I could potentially like, or Niche-Games. Its okay to seek out broken games with false advertising or the like, but when it comes to actual quality, rating and enjoyment, I want to read opinions of other players like me. I want to read how other users liked or disliked the title, not some 3rd party Schmuck descending from his throne, telling me what gets released and what doesnt.
Its lazy to blame Valve when you were actually dumb enough to buy Ride to Hell Retribution (Never played it, but from what I could gather it was functional, but jsut offensively bad), when you're literally three clicks and a Google Search away from thousands of people telling you that it sucks.
But, again. I agree that there should be a way to counteract outright broken Games, and that Valve could definetly up the quality of its service by providing one.