That was a big revolution at that time everyone loved to experience to play games, and more over games were very appropriate for all ages groups
But as the demand in the market grows with the latest technology and graphics games were also changed as per requirement so therefore unfortunately parents have to select the games for the kids nowdays as per rating of the game.
Then after taking feedback from the markets game manuafcturers started putting a ratings system in top of the game to help the parents to select the right game as per the kid age.
So for your information games ratings are as follows if EC exist on the game it means game is best suitable for Early Childhood , if the rating of game is E it means it is for everyone, if the rating is E10 Plus it means the game is suitable for 10 years and above,  for the teens the rating is T, If you are mature means above 17 years the rating is M, and if the game rating is A O it means game is only for adults not for childrens.
All above game ratings are clearly printed on the front of every video games available in the market or on online games.
Some of the best suiting games for childrens are Pac man, Super Mario Brothers, Mario Cart, etc and moreover these kid games have no violence.
Teens rated games are made for Teens but personally every parents should have a look what child is playing is it the appropriate teen game for her.
The Mature games are related to fun and excited games.Mature rated games are made for adults only.
Many a times when you want to play these mature games online websites first confirm that are you above 18 years of age then only you get permition to play game.