"sure shots" that we are confident will become popular. The incentive to do this should ideally be fixed, somehow.

It is, by competition. Not everyone can vote for a sure shot, and there can't be that many sure shots, so the more people are looking for them the harder they are to find (and profitably upvote). As long as they are easy to find that means the "mining difficulty" is low and mining is profitable. Do more of it.