One approach to favour more-liked posts is to take the sum of the squares of the likes, and then divide by number of posts.
I do wonder if my mistaken take might have value: to take into account the number of distinct liking accounts. It might for example help against cliques or voting rings.
In passing, I note my forum only elected 13 winners of a possible 24 new user of the month badges in the past 12 months.