It is fairly common knowledge that Jesus Christ was from the Middle East and so would have looked more like the picture on the right than the more familiar depiction on the left.
But what many people do not know is that the images we tend to think of when we think of Jesus, such as these…
….are actually pictures of Cesare Borgia, son of Rodrigo Borgia, Pope Alexander VI, and brother of Lucrezia Borgia. Machiavelli wrote The Prince about Cesare Borgia. Pope Alexander VI had all previous depictions of Jesus destroyed in about 1492, and replaced with images of his son. Henceforth, these have been the images used to depict Christ.
I was never sure why Pope Alexander VI did it, but always assumed it was to place his stamp on everything he could. He, after all invaded many of Italy’s city states, married his children to Spain, Naples and France in order to extend his power, bought the Papacy by means of bribery and corruption, legitimised his children, had multiple mistresses, committed murder. Rumours of orgies and incest also abound.
Having done a search though, I found this, which I think is probably the most likely reason
1492 goes down as the year that the entire planet was hoodwinked by the Roman Catholic Church. During Alexander VI’s term the Christians were fighting the Holy Crusades against the so called infidels. The enemy that the church was fighting was the northward movement of Islam as far up into Europe as Germany. These Middle Eastern Islamics took control of Constantinopole in Turkey and threatened the stronghold that the Roman Empire and in turn the church had on the world at the time. Pope Alexander used the age old tactic of discrediting an opponent to weaken his position. One major obstacle that faced Alexander and the church was the fact that Jesus, who their entire religion was based on was physically the same as the Islamics that they were fighting against. He was represented in all paintings, carvings and sculptures as the dark skinned man of Middle Eastern origin that he was. Nazareth certainly was in the Middle Eastern area that later came under the influence of Islam. How could they possibly convince their constituency of the wickedness of the enemy when their own messiah looked like them? Although the original Christians were certainly Middle Eastern people of color, by the time Alexander ascended to the papacy, Europeans had long taken control of the church. Pope Alexander VI’s solution was to have every image of the real Jesus destroyed and literally had the Vatican gutted and redone. He commissioned Leonardo Di Vinci to recast Jesus in the image of his son Cesare Borgia with the express intent of passing off historical Jesus as European in appearance. To this day, there are armed guards stationed around the clock at the entrances of the catacombs to keep anyone from viewing the original wall carvings of Jesus in his legitimate ethnic representation. (source)