Depends on the type of bike. Road bike, I feel the average cyclist can maintain 20mph on a paved trail. Mountain or hybrid, slower of course due to the higher rolling resistance of the tires. If you can't maintain 20mph on a road bike riding on a paved trail or road, I don't think you're a "cyclist."
And if they didn't, after being passed by someone going 25mph without forewarning you, and having the crap continuously scared out of you, you'd be making a thread here, "why don't those damn cyclists have little jing-jing bells to alert people that they're coming?!"
I used to run... competitively. If your miles are anywhere near 7 minutes in a 10k, like the rights to the term "cyclist" I posted above, I don't think you've got the right to use the term "competitively." Anything above 6 minutes per mile, and you're not finishing anywhere near the front (for a male, under 40).