Poker between a group of players is a zero sum game, therefore, the hypothetical "average" player breaks even.
This is not necessarily true. For example, it is not uncommon to have one or two really bad players at the table feeding the rest of the game. While the "sharks" may have the largest edge, the average player may have an edge as well. The inverse is also true. One or two exceptional players could be the only players at the table with an edge.