Dark Sonic is the most overrated thing since Shadow the hedgehog. Basically, he's just a black recolor of Super Sonic without pupils. I don't see how something that only appeared 20 seconds in an episode of Sonic X could be so popular. It isn't even a real form... I personally think Darkspine Sonic is way better.
Actually, Dark Sonic is not just a recolour of Super Sonic. Dark Sonic is the result of Sonic inducing the negative energy of the Chaos Emeralds, (or in this case, negetive power of multiple fake emeralds) while Super Sonic is the result of him inducing the positive. Dark Sonic is more vile and is clearly the cause of Sonic's negative emotions. As for why he's so popular, it may be because he is only shown for a few seconds, and people would like to see more of him.
I think it's pretty obvious. Right after Sonic sees the fake emeralds, he says something along the lines of "feeling a sudden chill." I don't think that they would make him say that for no reason. I'm Sonic Adventure, Chaos uses the negetive energy of the emeralds to turn in Perfect Chaos. A clearly evil or "dark" creature. During this Tails also tells Sonic that he can use the positive energy to turn into Super Sonic. So what if Sonic used the negetive energy of the emeralds? Obviously, Dark Sonic, or something similar. As for Nazo, I personally think it was a design for Hyper Sonic before the fanbase got their grubby hands on it.
I mean , think about it * nerd mode activated * Metarex are hard to beat by themselves and Sonic sometimes needs help from another teammate. those two METAREX Gold and Silver, were made specially for him! And he tore them apart with Dark Sonic using the FAKE CHAOS EMERALDS XD DARK SONIC WITH THE REAL EMERALDS COULD PROBABLY SPLIT THE PLANET IN HALF XD * nerd shutdown* you can't stop the nerd XD
I don't think the real Emeralds would make it really different. The fake ones created by Metarex seemed to have the same power output despite being really fragile. And Sonic absorbed the power of about 500 fake Chaos Emeralds or so that time(correct me if I'm wrong, it's been a while I watched Sonic X).