A shoutbox conversation inspired me make this post. I have come to the realization of when in my mind a person becomes decent at an Arcade/MAME game.
You see, almost all Arcade games have a certain point in the game where the game goes, "OK that's enough, it's time for you to get off the game", and amps up it's difficulty level. Now for certain games, this isn't necessarily the hardest part of the game, it's at a point where they want to kick the casual player off the game. Some games have a, "That's enough decent player, it's time for you to get off the game" part as well.
So here it is. Where you are transformed from being a casual/mediocre player to a decent player is when you get more points after the game kicks into hard, than before.
So here are some scores from different games that I know of where I would consider the score to be "decent."
Donkey Kong
A person can get around 85k before the level 4 springs. So a score of 175k in the game is decent.
Donkey Kong Junior. An average player can get around 110k with basic point pressing before the level 4 spring board. So a score of 225k in the game is decent.
Donkey Kong 3. A person can get around 150k before Donkey Kong starts throwing coconuts at you at the blue, and grey boards. So a score of 300k in the game is decent.
Moon Patrol. A person can get 75k before the tricky boulder stage. So 150k in Moon Patrol is decent.
So there are some examples. So yeah, it seems like a good rule of thumb for me.