It's easy to think that we're not running quickly enough. If you see people finishing a 5K in 15-17 minutes and it's taking you longer than 30, it's easy to think, "They're twice as fast as me, I'm really slow." Remember that you may be slower than that handful of people, but you're faster than all the people in red. That represents about 95% of US residents who don't run 5Ks, 10Ks, half marathons or marathons. You may be slower than Ryan Hall, but you're faster than 95% of people in the US.
I don't know how often you can say you're in the top 5% of the population in anything, but I don't get to say it that often. Just by signing up for a 5K and completing it, you're putting yourself in a category with a small portion of the entire population. Congrats!!!