In the current model of delivery, promotion of valuable content is not as easy as the value of the content might suggest. In fact it's quite difficult. Marketing (promotion) to the rescue. But the problem with marketing is that it costs money, which creates a barrier. Without wanting to detract from the skill and hard work of advertisers and other promoters, I would prefer a world in which such activities were not necessary.
So how would that world work?
What's needed is more organisation and some volunteers. Each volunteer would sign up to review X amount of content per month (where X could be number of pictures, minutes of video, minutes of audio, etc), of particular genres (tag-based rather than discrete categories). Submitters would be allowed to submit Y amount of content per month, with Y increasing with successful submissions, falling with unsuccessful submissions, but never falling below a certain minimum (everyone, no matter what their past crimes, should still have a voice). Ideally (and this would of course depend on number of voluteers and the amount they volunteer to review, and the volume of content), each piece of content would be reviewed by multiple volunteers.
Additional tiers of volunteers would review anything with an aggregate positive review emerging from the tier below. The number of tiers would likely need to be higher for popular genres. Out of the top of the tier hierarchy emerges a quality content feed that non-volunteers could subscribe to (via email, RSS, etc).
What would motivate the volunteers?
Volunteers could potentially be motivated by some kind of points system for "finds" of quality content.
How does this differ from existing mechanisms?
By creating a distinct volunteer class it segregates the audience between consumers and reviewers. Although any consumer could chose to become a reviewer, the commitment that goes with it would (hopefully) instill responsibility.
A more responsible reviewer class that happened upon content that was mis-tagged would be more likely to redirect it to an appropriate reviewer, rather than that content falling ignored by the wayside.
A more responsible reviewer class would (and would be required to) give feedback to the content creator, helping them improve the creative process.
The volunteers would become experts in their niche, able to spot plagarism and also identify true original content.
No content should go unreviewed.
N.B. The irony that is post on being heard will likely not be heard is not lost on the author.