It is only a fetish if all of the following apply:
A) It is sexual in nature. Having an interest in something because it is pretty or beautiful or is pleasant to the five senses does not automatically make it sexual. It is only sexual if it causes sexual thoughts and physical arousal.
B) It is the ONLY thing that can turn you on. If you are turned on by other things as well then it is an interest, NOT a fetish.
Since feet seem to be the dominant fetish I will use them for the example. Note: "normal" refers to the societal norms for what people are "supposed" to be turned on by to the exclusion of all else.
Beautiful, attractive woman is relaxing on the beach:
Man 1: Is aroused by her breasts, butt and feet.
Man 2: Is aroused only by her feet and ignores her breasts and/or butt.
Man 3: Notices and stares at her feet, but is not aroused.
Man 1: Does NOT have a fetish because he is interested in and aroused by the "normal" parts, as well as by her feet.
Man 2: Has a fetish because he was NOT interested in and aroused by the "normal" things. He was ONLY interested in and aroused by her feet.
Man 3: Does NOT have a fetish and is NOT even being sexual. He just appreciates and admires the beauty of what he sees.