I've just bought a C64 breadbin again after years of not having one and will take the time to get acquainted with the early games that I played back then. I've also got a 1541 disk emulation device that seems pretty solid loading disk images. Though testing it out with a game as bad as Cobra probably wasn't a great idea!
The C64 had the best sound chip of any machine of the 80s, including the consoles. It also had the worst colour pallette and a high colour mode that used rectangular pixels which meant you couldn't draw faces on sprites with any detail, stripping a whole layer of personality from games that its British rival the Spectrum had. For shoot em ups though, that didn't matter, because spaceships don't have faces! When all is said and done, if you want to understand the 8 bit genre, you have to play the Commodore 64, pure and simple.