My favourite way of judging movie quality is checking what kind of movie goers hate it and why.
-Pretentious watchers hating on summer blockbuster movies
-Political things and review bombs
About your specific example Steam comes to mind, they have a great review timeline feature that allows to filter out review bombs.
One feature that would be nice would be a filter to filter out reviewers based on certain criteria
-only one review
-only has reviews on certain films
-account life is less than specific threshold
That DB query is probably too expensive to run on a free site though. An app that scrapes the RT reviews and filters out based on this criteria has been on my list of things to build.