NOTE: 1 game is a full match of between 6 and 11 rounds (first team to 6 wins).
Just keep playing as a Human to eventually unlock this achievement, so long as each game has at least 4 players on each side. If you leave the game early it won't count as a game so just stick with it.
However if the server leaves (usually the player with the best connection) then that game will end and it WILL count.
There is no way of finding from the game how many games you've played, so you'll have to either count it or do a bit of guesswork.
The best way to boost is to find at least 4 people for each team and keep starting games. At the start it will say who is the server. The server then quits the game (after just a few seconds) and everyone gets +1 to their games played. Then just re-invite that person to the lobby and repeat. Far faster than playing 100 actual games.
If nobody saw who the server happens to be, you can find out when you try to quit. It will normally say something along the lines of "Do you really want to quit?" but if you are the server it will tell you it will end the game for everyone. Everyone needs to try to quit but only accept if they really are the server.