Rarely can we put numbers against these characteristics. Beyond the usual easily-defined parameters like player count, game duration, and recommended minimum age, we have a hard time quantifying things like the difficulty level of a game, its replayability, or its degree of player confrontation. We rely on game reviewers and fellow gamers to make qualitative, subjective assessments of these other, hard-to-measure aspects of games.
Lately I've been giving some thought to this question, and I'd like to try to develop methods for measuring some of these characteristics with some degree of objectivity. This task won't be easy, but it makes for an interesting exercise, and I hope it will prove illuminating with respect to game design considerations.
Next post on this topic: Luck vs. skill