This isn't really a review. I wrote this game, and I just wanted to point out one thing. I have never played Xecutor or even heard of it before coming here.
I've checked the game out on YouTube since reading the other reviews here, and I have to agree that it's really spooky how similar the two games are. Xecutor's graphics are better - mine are what you get when a programmer does the graphics! But I think Ano Gaia runs a lot smoother; it manages a rock solid 25 FPS - with real speccy hardware of course - which gives it a really Arcady feel. Your emulator may vary...
Oh, and the game was mainly inspired by Zynaps, but I wanted to do it in a vertical format.
By the way, I left a rating of 3 - Average. Just so that I don't muck up the ratings. :-)