What is so bad about Meg Griffin?

That is relevant, but no, I do not. Being a fictional animated character, Meg never ages. Assuming an episode never calls for it, her skin will feature no blemishes, scars, zits, or anything that could be considered negative by most people. For me, such things will likely be inevitable.
In this light, Meg Griffin has an advantage over all people, really. I suppose in that context, I ought to compare her to an ugly animated character if I wish to prove my point that she is not an ugly person.

So you're uglier than Meg Griffin.