Most CRPGs start the players out as level one schlubs. Rats and wild boars are a major cause of death among level one characters. As they defeat these rather modest enemies and advance the story they gain in levels; they get new equipment that adds to their stats. By end game they are a walking engine of destruction, almost invincible save for the end boss or falling asleep at the keyboard. Measuring progression by level is part of the problem.
CRPGs are the descendants of tabletop RPGs and those trace their roots back to Dungeons and Dragons. Early D&D had its own roots in tabletop wargaming. D&D used level based progression, and thus CRPGs use it today. But there are some serious mathematical issues that can come from this scheme. I recall two games of Robotech back when I used to play tabletop games regularly. One gamemaster followed the developer's advice of parcelling out experience points, which are used to determine the player's level, very sparingly. In his game it took six months to a year of regular weekly play to hit the next level. The other gamemaster handed them out like candy on Halloween. His players quickly passed the level that the designers recommended for character retirement (the player character becomes a non-player character used to introduce adventures by the GM) and on to the level cap. Characters in Robotech really weren't designed to be played at that level. A single five player party would take on whole alien armadas - by themselves. This is roughly the equivalent of five soldiers winning World War II. My Fallout 3 game on the PS3 has reached this point. There really aren't any enemies that are a threat to me anymore, and that kills a story dead.
I think there might be a better way of handling progression in computer games. Imagine if we turned this equation upside down. The player begins as a major hero - at the "level cap," they are well skilled and equipped - we can skip killing 1,000 boars for experience. The game designer uses this period of nigh invulnerability to teach the player how the game works. Over time though, the player gets progressively weaker. His stats and skills don't go down, but his equipment starts to wear out, in a modern game ammunition might become scarce. This reverse progression means that enemies don't have to scale upwards as dramatically as they have to using a more conventional progression scheme. Players have to make choices about when they want to use their equipment - they're less likely to pull out the +12 Sword of Awesome or the Man Portable Nuke Cannon against the diseased rat if they know it might not be available against a more threatening monster. I think this system allows more freedom for the writer - players out leveling content is less of a concern.
