Main reasons would be the appearance of the competitors i.e. men competed naked for pride and toughness. Another reason would be the sports as the ancient Olympics consisted of at most ten sports. The modern Olympics have substaintionally more events adn soon increased throughout the ages! in ancient Olympics athletes who won will have a lifetime supply of foods, in modern Olympics victorious athletes will have medals .. and the modern Olympics now have winter Olympics , there are more sports than in ancient greek the ancient is a preparation for war but the modern are sporting events
Some of the differences were:
The ancient Olympics were held only throughout Greece, for Greeks; the modern Games are held around the world, for people of every nation.
The ancient games allowed only men to compete. Competition was performed almost nude. Wars were put on hold for (and sometimes, even decided by) the ancient Olympic games. Winners were often awarded expensive prizes, including land and olives (a precious commodity in ancient times).
The modern Games, until recently, had strict requirements about being an amateur. Both men and women compete, though separately. They were canceled during the World Wars. In 1980 (Moscow) and 1984 (Los Angeles), a substantial number of countries boycotted the Games, which in ancient times would have led to out-and-out war.
In addition, the modern Games have a winter sports program; the Winter Games used to be held the same year as the summer edition, but as of the Lillehammer (Norway) Games of 1994, they've been shifted by two years to be held on the even-numbered year that falls between the Summer Olympic years.
In ancient times:
Wars between all competing nations would end, competitors were only men, there were only summer games every 4 years, only at Olympia (never changing the venue), very religious event, most events were nude, women were