There is not, no. Should there be? My preference would be no, based on the reasoning
@IcomIcR20 gave.
From personal experience as a dbadmin for a number of years, I have found that some of the most dependable, meticulous submitters are not necessarily prolific contributors, but instead will put together a well thought out submission that almost never requires any further vetting or followup. On the other hand, some of the most prolific submitters I've dealt with tend to be sloppy and inaccurate, requiring more effort on my part to elicit further details. And yes, some submitters are already in the bad habit of making multiple submissions when a single would be more appropriate. Either they believe that all five talkgroups they're submitting at the same time for the same system require their own submission (they do not), or they are in such a rush to be the first out of the gate that they'll submit things in a stream of consciousness while listening live, rather than exercising some patience and restraint to instead create a higher quality submission.
I don't see much value in having a leaderboard for this sort of thing, and frankly I don't see it resulting in the encouragement of
good submissions. Human nature being what it is, it would likely only attract the wrong kind of increased activity.
I've made it a point to periodically thank those who contribute regularly or dependably privately, and to let them know that their contributions are valued and appreciated. I obviously can't speak to whether or not that alone is enough recognition, but they continue to contribute, so I reckon it is.