Gyruss came out pretty late in Nintendo's 8-bit life, 1988 in Japan and 1989 in the U.S. By then, most Nintendo players had become used to more detailed games like the Megaman and Super Mario seres. This may explain why Konami felt compelled to juice Gyruss up a bit, adding more levels, new weapons and power-ups, and even new boss battles. All of these additions don't really improve the game. They don't necessarily make for a bad game, either, but they do get a little in the way, especially if you would rather play Gyruss as originally designed. At the very least, an option not to have boss battles would have been nice.
Despite the potentially distracting additions, NES Gyruss is a solid port, right down to the theme music. The graphics aren't quite what arcade players will remember, but at least the audio and game play are decent. The game is worth a look, if not exactly something to appeal to the purists.
Grade: B-.