Born in the wrong era? No. There is no wrong era.

here are the few games that i know to be played primarily at a playground.
i believe that the playground is the place to build the foundations of your athletic ability, and from there to further hone your skills.
it is also one of the first social gatherings for children outside of nursery skool.
here are the games that i know of.
this list is definitely limited, and if i could i would very much like to continue to play these games, even now. if ever anyone knows of other games that you personally enjoy which have not been reflected in this list, please let me know.

The List
(note: rules are flexible, these are merely the main rules)

1. Blind Mice
catcher cannot open his eyes. everyone else cannot touch the floor.
-trains largely finesse and sense and composure
-Crocodile variation: catcher can open eyes when on the floor

2. Good Ol' Catching
count to ten. catch anyone you can.
-trains reflexes and stamina and speed
-variations include block catching and bicycle catching...etc

3. Police and Thief
mulitple 'police'. when 'thieves' are caught, they go to a designated 'jail' area until another thief can free them by tapping them.
-trains reflexes, strategy and stamina

4. Ice and Water
when caught, 'waters' must 'freeze' until another 'water' taps them and melts them.
-trains reflexes, stamina and strategy

5. Poison Ball
throw the ball to catch someone.
-trains accuracy and reflexes

as can be seen, the following activities largely train your stamina, and reflexes adn speed. these are essential qualities of most sports. hence by training from young you can become the ultimate athelete.
think, blind mice gives you the finesse needed in gymnastics, catching, the speed reflexes and stamina in most ball games, police and thief, the foresight in stratgy and evasion and teamwork in catching.
this is ingenious