So Why don't the media refer to Kim Jong as President and instead,they refer to him as North Korea Leader?
He wasn't elected. A president is generally elected. A dictator is not a president. It is important to distinguish just what kidn of leader a person is and what kind of government they are head of.
I saw it reported on Fox News that it was a "meeting between two dictators", which was inaccurate... even if Trump wishes he had the powers of a dictator.
It is just semantics. The word "president" is from the Latin/French and is the person who sits before, presides over, the leader of a group, the chairperson. Many nations use that title, including Cuba. Nearly all of the heads of state hold a title that, like "president", boils down to "leader" or "guide" or "chairman" in their respective languages like Führer and Il Duce. Kim-jong's grandfather, Kim Il-sung, held the title Great Leader and posthumously was named "Eternal President".
It is the same with "democracy". After the Divine Right of Kings lost credibility, every nation has since claimed the fiction that its power arose from The People and that it is a "democracy", the USA included. Our own nation is in practice and in fact an oligarchy. We don't elect our own president, the Electoral College does. Drink the Kool-Aid if it makes you feel any better.
So that's the reason the stamps won't stick.
Some countries have a President. Some have a Prime Minister. Some have other titles. A quick Google would indicate that Kim Jong-un's official title is Supreme Leader of the Democratic People's Republic of Korea.
Not that there's anything remotely democratic about an oppressive regime, run by a family that automatically hands on the leadership baton to the next eligible family member in line. I don't think it's particularly wrong for the rest of the world to drop the 'Supreme' element when referring to him.