Who decided to have the 7 wonders of the world?

Answer 1

All of the wonders of the world were not made by one person, however:

This link may help you - http://en.wikipedia.org/wiki/Wonders_of_the_World

It provides information about who made them and so on...

Some of the wonders of the world are natural and therefore no one made them.

Answer 2

There are several sets and each has its own origin. "The" 7 wonders are a set of the ones most often included in the various known sets. They've also branched off into "The" 7 (manmade) wonders of the ancient world, the modern world, "The" 7 natural wonders etc