I choose Oersted because he showed how a current-carrying wire behave like a magnet. Without him, the other scientists that you mentioned would not be able to formulate the Electromagnetic Wave Theory.
Guys, for me Ampere is my favorite scientist because he demonstrated the magnetic effect based on the direction of current. Who is your favorite guys?
Wow, that's a great achievement but Faraday is awesome because he formulated the principle behind Electromagnetic Induction.
It's Maxwell who is the most awesome of them. He contributed in developing equation that showed the relationship between electricity and magnetism. He is a brilliant scientist.
I like Hertz because he showed experimental evidence of EM waves and their link to light. Even the unit of frequency is named after him. He is awesome.