It was a memorable game for him but he and his team-mates were helped by some poor defending from Birmingham.
Robbie Brady's defence-splitting pass set up Boyd's opener before confusion between Blues centre-back Steven Caldwell and keeper Butland allowed Gedo the chance to race through and double the advantage.
Hull were creating chances galore and, despite being off balance, Boyd soon added the home side's third before Koren made it four from long range.
Ahmed Elmohamady's whipped cross set up Gedo for his second and, despite Birmingham's late goals, Hull manager Steve Bruce was able to enjoy a very easy win against his former club as his side leapfrogged Watford and closed the gap to leaders Cardiff to five points.
Hull boss Steve Bruce:
"If there has been a better home debut, I haven't seen one for a long time. He [George Boyd] was terrific from first to the last.
"He's a good player. You can talk about tactics, formations and systems but this kid oozes ability.
"He can play with anybody. He's a clever footballer. He's made the difference today at an important time."
Birmingham boss Lee Clark:
"It is a tough place to come and when you are 30 seconds in and 1-0 down to quite a simple goal it is a tough one.
"From there it went from bad to worse and we were 3-0 down in half an hour. They were not great goals from our point of view - awful in fact.
"The first two are just down-the-middle goals, basic defending. We knew we would come under the cosh against them, they play high tempo, I don't think it was down to our system or tactics."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.