Compare a typical cover band to the original artist. The songs are catchy, the players know their instruments, and the vocalist does a decent job impersonating the more popular singer. The cover band delivers a good time, and yet for all the members' talent and skill, they just can't replace the original. That's what playing NES Defender II is like.
Granted, comparing a home console port of an arcade game to a cover band is a little unfair. After all, a home console typically cannot duplicate an arcade original, particularly a home console from the 8-bit era. Usually, however, you can still see the essence of the original in the home port. With NES Defender II, it feels like the inspiration was some knock-off of Stargate, rather than the actual Stargate. Several enemies are missing, particularly Pods and Space Guppies. Other enemies behave differently, such as the Dynamos' Space Hums, which no longer home in on the player's ship. Humanoids do not have to be brought back to land when rescued. The Stargate does not offer a shortcut to humanoids in danger. And so forth. None of these differences are due to technical limitations of the NES, and so the changes don't seem necessary, just different.
Despite the differences, this version is still fun to play. It just doesn't feel quite like Stargate. More like, Alien Defense Game as Made Famous by Stargate.
Grade: B-.