Based from my observation, a lot of coins now are launched using the ethereum platform. My instinct says that they are just using the name of ethereum to grab some cash from naive people. So my answer is no, not all currencies created thru ethereum are legitimate and authentic.
I don't think so, because even before the days of ethereum getting more popularity as now several projects have been functioning based on the ethereum platform. Now too the success is continuing and just because they have grown we cannot say it's a way to grab cash from naive people.