In roguelikes you can often eat what you kill. You often gain stat bonuses and powers from eating appropriate monsters.
A character in a game I played was concieved as a crazed halfling chef who would cook anything that he killed. However the GM was revolted when he started barbecueing orcs, and threatened to slap alignment changes on all of us.
In Midnight, dwarves have a custom of eating fallen orc foes, both from neccessity and as ritual.
The definition of cannibalism in game must be related to the cultures of the game and the sensibilities of the players.