Vocabulary – Is There a Noun for a Man Who Wrote a Best-Seller Book?

You mention two different use cases.

an eye for detail in arts ... an eye for detail, which is why a photo was taken from the right angle or perspective

Like jimsug and ChristopherW, my immediate inclinations are meticulous and keen- or sharp-eyed. I don't know of a single adjective (or even a concise phrase) which has this meaning and also carries a specifically artistic connotation. I can only recommend general terms and suggest that you add modifiers to specify the artistic bent. Other potential choices:

• Assiduous
• Sedulous
• Scrupulous (very often used in a moral or ethical sense)
• Fastidious (very often used when speaking about cleanliness)
• Detail-oriented

an eye for detail as to what is the cause of a conflict (something which other people hadn't seen yet)

For this case, I'd use astute. 1, 2. It applies specifically to situational assessment, and I would not use it to describe an artist's attention to detail, e.g. when painting or composing a photograph.

It's kind of a broad question since people may like to listen to someone speak for different reasons, adjectives used to describe a good orator are

eloquent
articulate
knowledgable
engaging
charismatic
well-spoken