Have you ever observed what your eyes are doing while looking at a picture? Do you observe a difference between looking at interesting and boring pictures?
A picture is nothing more than a flat representation of the 3D world in which no objects exist. It is pure colors, textures, shapes, and lines. So, the question is “what is a good composition that makes a picture attractive?” There is of course no simple answer, otherwise everybody would shoot perfect pictures all the time.
Bruce Percy wrote a nice book about that: Simplifying Composition, in which he explains how the eyes flow over a picture. Most people when they look at a picture they start between the bottom and the middle left and then explore the rest of the picture. It turns out that lines in the pictures may lead the eyes to different parts of the picture. Have a look at the picture below.
What in reality is a road is in the picture a line which takes my eyes from bottom left along the diagonal line to the middle right of the pictures; after that my eyes come back via the repetitive vertical lines (the trees on the left of the road) to the contrasting colors. Finally, my eyes travel again along the repetition of the vertical lines (the trees on the right of the road). This may repeat itself a couple of time, every time discovering more details. This makes a picture interesting.
Lines can be as simple a road, a horizon, a cloud formation, however, they can also be imaginary lines between areas with similar shapes or similar color, or a repetition in texture or shape. Of course, most of the time the lines are not straight, they are curves in various shapes. S-curves cause a strong pull. Think of an S-curve of a river.
Next time before taking a picture have a look at how your eyes flow over the scene to see how interesting it is. Maybe a different position or angle will improve it.