I would like to know why some images get 3000+ likes on website like 500px. What are the parameters behind those likes?
- Shot mode (M, A, S, P) etc.
I can understand subject and composition matters a lot, but does Mode also matters?
The parameters which matter:
Whether or not an individual considers a photo worth a like is dependent on a lot of things:
the quality of the photo (and how important the viewer thinks that is)
the subject matter (and whether that interests the viewer)
the mood of the viewer
Very few objective properties of the image will be relevant.
I'd argue that what makes a photo good isn't necessarily what makes it popular on a photo sharing site like 500px.
I'd consider most of the "top" content on 500px to be essentially viral content which could be popular for any number of reasons like humor, politics, special effects use, surprise, popular location, and so on - which may have nothing to do with if the image is good or not. In addition, the 500px site itself has algorithms that determine what content will reach each user on each page - again which may have more to do with the viral nature of an image and less to do with it's actual quality.
To directly answer your question, images are popular on 500px and similar sites based on the specific criteria that the site employs. For more information on 500px specifically see their help article on Pulse and Views.