What are the smartest games you can play with two people? Games like Chess and Go immediately come to my mind.
What about 4 people? I can think of board games like Scrabble and Catan, card games like Bridge and Poker and game shows such as Jeopardy.
What about a room full of people? Such groups have to resort to games like Bingo, Housie and Tombola.
If you notice a pattern here, the larger the number of players, the more the game needs to be dumbed down to accommodate everybody.
As a rule of thumb, the larger the group, the lower the quality of real-time interaction it can have.