It really depends on which sport or video game Your playing. If your on a 3dsXL, and you play Mario Kart 7, You can have 7 or 8 people playing. if your playing soccer, each team needs to have an equal amount of members. if you have 10 people that want to play soccer, devide them into 2 equal groups.
12 players
6 players
4 players or a computer that does the 4 players
25 players
8 players
7 players
11 players
about a million players
30 players
nine players
Two players
17 players