Definitely depends on the game. Every game on Neo Geo Pocket Color, I spent 2 days practicing, 2 hours recording and got the WR. Maybe 90% of games across all platforms get 0 to 2 runs submitted per year. They aren't very competitive but sometimes that one run is difficult to beat. Other comment has good point that most games don't have many unique runners to begin with.
There's no average that can apply to 100 runners in the most competitive and popular games. At the elite tier, 1000+ hours is common. Years of practice unless you're a prodigy. At a relatively low 10 hours per week, you're looking at 4 years to hit 1000.
At a relatively low 10 hours per week, you're looking at 4 years to hit 1000.
That's 520 hours per year. 520 * 4 = 2080. You'd need 2 years, not 4 years.
Anyway, my most run game has 1800 hours by myself, which includes casual playthroughs, glitch hunting and other stuff. My second most run game is at ~700 hours minus TASing, though I haven't played it in a while.