My most liked posts are my photography posts.
My assumptions are that readers mostly read other’s posts on WordPress reader. Photographs give them an instant view of what they are going to get. It’s easy to like them then and there without clicking for the original post.
Second place is taken by Friday Fictioneers. They are just 100 words posts. Easy to read and if they attract your fancy then comment.
I always give a good photograph to compensate for my writing. So the third place goes to quotes with lovely, eye-catching photographs.