I'm rubbish at Stargate - I'll admit that from the off. I'm rubbish at Defender, too. That doesn't stop me from returning to this time and time again to get myself thrashed by a proper old-school classic. A few things are added that make me favour Stargate over its parent - a greater variety of enemies, a cloaking device, highly random hyperspace power and of course the Stargate itself, whose function changes depending on the game situation at the time.
I've played plenty of variants over a lot of platforms over the years, but when it comes down to it Stargate is one of those that doesn't really need any updating, and it certainly doesn't need any graphical embellishments. Having the onscreen action looking relatively simple is a blessing in something so insanely intense.
That doesn't mean it's not pretty though. Multicoloured enemies zip around the screen, explosions are glorious bursts of particles, and of course the laser is probably one of the most satisfying weapons to grace a shoot 'em up. Couple all this with the wonderfully raucous sound effects and you've got yourself the very essence of arcade gaming.