There's a whole lot more at play to that study than Good Looking, Average, and Ugly. There are a bunch of other factors that say a lot about the people.

I made this into a separate topic because it would be interesting to discuss these concepts in greater detail.

Here are my thoughts:

First we will be dealing with the average guy: http://i.imgur.com/HjVGuVD.jpg

Night time, shitty lighting, flash directly to face, horrible background.

Do not take pictures like that. I'm not gonna write a tutorial on how to take good pictures when this topic has been dissected by professional photographers to an extraordinary level.

This guy needs to tame his eyebrows, especially near his nose: http://imgur.com/ASF4sll

Look at the average guy's collar. It's all curled on one side and flat with a big crease on the other; looks like shit. His shirt also has way too many folds, he needs to reduce that like so: http://imgur.com/T9Py7ti and preferably get something like this: http://imgur.com/yQwYAXg http://imgur.com/taZvjl6. Look at the collars on those shirts too, those are nice. People, especially women, pay attention to this stuff.

His undershirt also looks discolored, old, and you can see a minor rip in it. He needs a nice new undershirt like this: http://imgur.com/GwfBnFS

Looking your best.

You may be ugly, but there's a stark difference between an ugly guy that looks like crap and an ugly guy that actually looks the best that he can look.

Let's take a look at the ugly guy: http://i.imgur.com/bWv7tvS.jpg

What's with the wide neck shirt? Did he shave his neck-beard or did he not? $3 sweater from goodwill, /r/whatcouldgowrong? Collar down, no up, no down, fuck it, it will be down in the front and up at the back. Hairstyle that accentuates already enormously large forehead, sure why not. Pale skin color with pronounced zits on face, check. Worst choice of glasses, check.

All of these things give signals. "I don't give a fuck about clothes", "I get my sweaters from goodwill", "I have no aesthetic upkeep whatsoever", "I love wearing pedophile glasses".

On a side note I can shed light on why girls think these kinds of guys are creepy, here is a girl's thinking:

He doesn't care about clothes, he really doesn't know what looks attractive on him and probably doesn't care. I care about clothes and I know what looks attractive on me, why doesn't he? That's weird to me. He doesn't take care of his neckbeard, zits, and his hairstyle doesn't fit him at all. His glasses look really unattractive and that makes me think that he doesn't care what other people think of him (subconsciously the girl will think that he doesn't get a lot of girls because she's turned off from him, and assumes that other girls will be too, at which point her mind will transition into thinking he is weird, lonely and etc.). (All of these factors will make him look "creepy" to her.). I can't trust him or like him because I don't understand him at all (I care about clothes, he doesn't, etc.) and I am physically repulsed by this.

Fix the zits, shave neckbeard, get nice shirt, get better hairstyle, tan just a little bit to not look albino, and what do we get?

http://imgur.com/xzQgRQp

Nearly the same face shape. Both have protruding monkey-type ears. Both lips are smaller and slant downwards (with Jonah's being more "full"). This is what "looking your best" is.

Going back to that side note about how girls see guys, here's what a girl would say for Jonah if he was a random guy and not an actor.

He cares about how he looks, I love that, I care about how I look too. I think he did great on his hairstyle and his skin looks great. What a nice boy, I could even date him, let's see if he can turn me on. I get him because him and I understand the same things "looking good is important" "looking your best is something you should try to look". I feel safe because I can connect and relate with him, he is not a creep.

Now let's look at the good looking guy: http://i.imgur.com/HvO1Qpf.jpg

Nice background √

Eyebrows plucked (or naturally good like that) √

Hairstyle works well, recently cut √

Face skin looking nice √

Collar looking good, polo material quality very high, nice brand, nice red and blue hue √ √ √ √

Photo likely taken in early morning (best time for photos because light outside is white in color (noon time it is more yellow) √

Wrist bands indicating free spirit, etc √

Non-lifeless death stare and facial expression √

Also take into consideration that Jonah Hill and the good looking guy care about their looks and appearance so they have a very high chance of being very clean people. Girls like clean guys (showered, smelling nice, etc.). The ugly guy has a low chance of being clean based on face value assessment, which will make the girls uncomfortable.