Well, the concept was interesting. The "god in mortal form doesn't know who he is" thing felt very familiar to me, but I can't remember ever reading such a story where the god in question was the god rather than just a god. So I think there was some potential in the basic concept. There were quite a few issues with its execution, though.
You mentioned that you've started writing in third-person now, and I think that is a good idea. The first-person viewpoint didn't precisely detract from the story, but it added nothing, and was therefore something of a distraction. The strength of first-person, at least in my opinion, is the way it can be used to really let us get inside the head of the main character. It can also be used to directly address the audience, and can provide foreshadowing of future events. Your story didn't take advantage of any of those things.
I wouldn't completely abandon the idea of doing a story in first-person. I'd just say that if you do, make sure you play to the strengths of that perspective.
The story didn't really grab me. Part of the problem is that I never got a feel for any of the characters, and part of the problem is that the dialogue felt rather stilted. Not just the dialogue, but the descriptions as well. Everything felt a bit too abrupt, it seemed like I could never really get a feel for a scene before we moved on. I think a big part of the problem was that you tried to cram a lot into such a short story. We get Crea's introduction, background info and setting descriptions, Troy's introduction, Troy's reveal as the Destroyer, the fight at the Water stone, the fight at the Air stone, the fight at the Fire stone, the fight at the Earth stone, and the climax.
There were too many different locations. Among various places we had a world in the clouds, a fiery hellhole, and a strange mountain land, but the limits of the short story format meant we got at most a handful of sentences describing these strange environments, and we left them as quickly as we arrived. I haven't read very many short stories, but I think they might work better when they are more focused. A full length novel can explore a whole bunch of diverse locations better, because it has the time to.
And finally, the story was a bit too predictable. It was pretty easy to guess that Crea was the Creator. At least it became easy the moment we found out that Troy was the Des*Troy*er. And as soon as the Water crystal was destroyed, I guessed that all the other crystals would be destroyed as well, and that the climax would occur after that. Sure enough I was right. This eliminated any tension during the battles for the crystals. I knew they were going to lose ahead of time.
This just added onto the other issues. Since I didn't care about the characters and could predict how the fights were going to go, I was tempted to just skip to the end, as there at least I wasn't totally certain what would happen. Not a good thing. Though at the end, you did kind of surprise me a little.
I figured that Crea would probably save the world and restore it, not that it would be destroyed with everyone on it dying, and he'd create a new world. So as I said, I was surprised, but I wasn't particularly happy about this surprise. The problem was the legend said the Creator was supposed to help the people. There were several times during the story where people said things like "The Creator will help us." Yet they all died anyways.
Maybe if there had been some indication that they lived on in some afterlife, or got reborn into the new world, I would have felt differently. But I never got any indication of anything like that, or even an indication that things would have been the slightest bit different for the people had the Destroyer succeeded in killing the Creator.
Maybe that type of downer ending was what you were going for, but it seemed to me that either the legend should have been worded differently, or there should have been mention of that fact that the Creator failed to fufill the legend. As the story is written, there is contradiction between the set up and the ending that is never explained.
Anyways, I hope those comments help. Hope I don't come off as too negative.