This includes box legendaries, The "Lati" twins, the swords of justice, the forces of nature, the regis, and every legendary in Pokémon. Note: Rounded to nearest whole number.
Based on this website: http://bulbapedia.bulbagarden.net/wiki/Legendary_Pokémon#Statistical_average
The average stats for a Legendary Pokémon are as follows:
S. A.: 116
S. D.: 106
I calculate these for the stats: