I developed a theory related to skill levels in games.
Basically there are 4 skill tiers:
Tier 1: The people that win most majors and are clearly better than most people at their respective games.
Tier 2: Pretty much Tier 1, but just aren't as adept as certain things. I'd wager that most people are at this level.
Tier 3: Know how things work, but not how to work them.
Tier 4: Button mashers, pure krogans, roll tier, etc. People clearly unfamiliar with the game that they are playing.
I've found that this applies to almost any game that has any sort of competitive aspect to it.