I've been trying to keep a relatively consistent approach to rating that's somewhat similar to Miniature Giant's approach. That being said, I did add some slight weighting based on uniqueness, displayed potential, tone. Original assets weighed highly for me, though I also appreciated the use of external assets that were well-implemented, modified, and didn't feel obvious/out of place. I also dock points if a game used third-party assets that weren't being referenced in any way. The polish piece is a hard one to evaluate on it's own though. A few of my favourites were impeccable, however they were also short and to the point, so I doubt they were things worked on prior to the jam. Now if they were dozens of stages long, it might get me wondering.
Basic metrics for me (though not exhaustive):
1- Non-existent (and not in a purposeful/effective way that goes with the tone/overall experience)
2- Fairly limited or seemingly minimal effort
3- Works fairly well and no major issues
4- Well made, cohesive, enjoyable
5- Inspiring / something I'd share with a friend
Edit: Forgot to mention - I go easy on bug issues, especially smaller ones / pieces of more complex systems. That being said, if it's unplayable for me after refreshing/starting over and comments also indicate that it was unplayable, that's definitely going to factor in.