While not up to the greatness of Gate of Thunder or Soldier Blade, I think it's a darn good shewty. Its greatest flaws are annoying shooting sound effects from some ship/weapon combos, slowish ships, its short length, and it being too easy to beat via continue spamming; otherwise it looks great, has huge bosses, rockin' tunes, and a nice variety of locales with fitting enemies.
It doesn't deserve the hype of "best shewty evah!", but that's only claimed by collectards that equate game play quality with price. It certainly does deliver on having varied and colorful backgrounds, lots of big sprites, and tons of animation.
Also, nando's right - in all probability you got a bootleg.