If we had a scale from 1 to 10, with 1 being a complete noob that's just figuring out how to drive, 5 being completely average, and 10 being outstanding, I'd expect the community to average around 7+. The rationale behind this is that message boards don't typically represent average and below-average players very well, but rather tend to have more of the hardcore variety, which tend to skew slightly higher on the skill-o-meter.
Personally, I'm not outstanding but I'm experienced and getting more so. Over the past couple years I've ramped up several times over in my driving abilities. In other games I've typically ranked at least within the top 10% on leaderboards, typically more along the lines of the top 5%. However, these have typically been on somewhat more arcadey racers, though in FM3 most of my fastest laps are within the top 5% on the boards.