There was an ancient witticism (I forget who said it) that the people who colonized Chalcedon were blind--they failed to notice that there was a much better site right across from them on the European side.
I have heard this as well. I always assumed the Asian side was picked because either the Thracian barbarians were roaming about on the European side while the Asian side was more settled or that the Asian side was where money was at the time - in other words the Chalcedonian colonies would get first shot at exporting the goods. If they were on the European side they would have to compete with other shippers arriving into Asia as well.