The number of women who want to fuck it.

If someone likes it, then it is good lookig

Every penis is unique and sexy in its own way, but a slight upward curve does the trick for both of us.

I've asked this question in a similar way; that is "What makes a cock attractive?" I do believe that beauty is in the eye of the beholder and hope that every man loves his own cock.

But here's some objective information:
The Journal of Sexual Medicine published a new study designed to answer a rather unusual question: “What is a good-looking penis?”

What Makes a ‘Good-Looking Penis,’ According to Science

July 28, 2015 | By Catherine DiBenedetto

The Swiss researchers who conducted the investigation asked 105 women (ages 16 to 45) to rate the importance of various penile traits.

Of the eight characteristics, girth and length fell somewhere in the middle of the pack (Nos. 4 and 6, respectively), while the top three qualities were—in order—“general cosmetic appearance,” pubic hair, and penile skin.

Other traits ranked toward the bottom of the list: shape of the head (No. 5), scrotum appearance (No. 7), and lastly, position and shape of the urethral opening.

and a little info from "Men's Health" magazine:
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I don't think that their are anything that determines an ugly or attractive penis.its how you see it.