In football, if you lose a game, that usually doesn't prevent you from progressing to the next game (the next level). Your record stays with you, but it only determines whether or not you make it to the playoffs (extra levels). Football allows the player to experience nearly all content regardless of performance.
That seems to be a model that could be transferred to FPS games and Action RPGs.
Perform poorly against most of the foes of one level, and you can still progress to the next level. Doing well in most levels will unlock some extra areas, while winning all levels will unlock an epic encounter or something similar, but the game generally moves forward regardless. And, like a football season, level order is not static. The player might face the swamp level first, last, or anywhere in between.
Applying this concept of "progression independent of achievement" seems easy enough on the macro level, but I wonder if it could also be applied to individual encounters.
In (American) football, if countless plays in a game go badly, that doesn't prevent you from progressing to the next play (the next encounter). Winning plays affects the circumstances of future plays (such as field position) and the role one must take in the next play (offense/defense), but poor achievement does not negate progression entirely.
The last quality is what might be difficult to translate into games other than turn-based games. How do you encourage skillful play of individual encounters without punishing failure by ending progression?
NCAA Football '08 does this largely through a system of momentum. Perform poorly and your enemy gets the momentum, making progression harder but still inevitable (not merely possible). This system increases the opponent(s)' attributes and skills -- something easily translatable to other genres.
Like field position in football, it would be great to see the FPS/RPG player's actions in individual encounters affect the setting of the next encounter. An enemy might be blocking a slowly closing pathway; meaning the player can sneak past the enemy or fight through (not necessarily killing) to the opening, but must otherwise take an alternate route. Or actions in one encounter might affect the availability of environmental objects in other encounters.
Anyway, just the random thoughts of the day.