Well, during the last 17 years i played all the console and coin-op shooters, and z-out is undoubtely one of the best ever in the r-type style, all systems included. Infinitly better than x-out too.
And i presume that you're going to tell me that it is an insult you tell you that someone pretending that z-out is terrible fell on his head ? Irony irony eh eh. But by reading you here i understand better the kind of guy you are. Shooters are my type of game (i am developping an universal game launcher, i tried ALL of them), z-out is perfection.
People also tend to forget that this gem can also be played at 2 simultaneously, and they shouldn't !