I think anybody can be a critic. What I really hate is when people are given criticism, and they respond with "Well, how about you make something better! Lol i pwn u with my original comebacks!"
Take a look at the most popular movie or other art critics in the world. Then try and guess how many can draw anything better then a few stick figures.
You don't need to actually be able to do better, you just need to be able to understand the principles behind what makes something appealing.