Sincerity of emotion in a photograph, as with any work of art, is often the most beautiful thing about it, whether we are directly aware of its effect on us or not. With portrait photography, or photos of people in general, this is especially prevalent. It's hard to deny the emotions and expressions of faces looking out at us, beseeching an interaction of the heart.
Landscape photography and events photography can have an effect too. Atmospheres of places and events resonate when captured by a photographer or artist who has taken the time to connect before clicking the shutter. When we are in tune...