This is mostly a discussion of semantics. Some are concentrating on it being a "good game", which puts focus on gameplay mechanics, balance, accessibility and so forth. Others are going on about it being a "good game", which is more just a descriptor of whether or not it's worthwhile, entertaining, or morally fulfilling(?).
The thing is, Cortex Command honestly isn't a good game. The balance doesn't even exist, the gold system is a complete joke unless it's changed recently, the AI is hilariously poor, walking is not only incredibly slow but also exceedingly dangerous (try clambering over terrain as one of those cheap humans. They're just as likely to rip their own feet off on a stroll as anything else), and the whole gameplay aspect is either so poorly implemented that it's nigh-impossible, or constructed to be so mind-numbingly easy that it's almost not worth it.
However, this absolutely does not in any way detract from my enjoyment of this gem. Indeed, the AI, wonky physics, and random unintentional acts of chaos have contributed quite a bit to my hours of gut-aching laughter spent tooling around with this thing. The gameplay is still very much in its infancy, and I actually quite like it that way (although I would love to see what this engine could do in a more developed and 'serious' endeavour).
I think I regard Cortex Command to be more of a 'toy' than a 'game', at least for the moment. It has great potential to become a good game, but it isn't. Not yet. What it is, however, is an utterly fantastic toy, and having played a number of 'toy' programs before, I know that there is absolutely no negative connotation associated with that term.
But whatever anyone's opinions might be, we're still getting up in arms about fun. Something's wrong in this picture.
I made a special level before, on a test map that was very short. I built a series of tunnels on top of each other with no connection from one level to the next. Then I implemented a special invasion force that consisted only of drop pods with zombies and skeletons armed with WW2 weaponry (plus a shovel to dig with). I then placed a heavy supersoldier in each tunnel, and waited.
The objective, of course, was to survive. Look a few pages back and you should find a picture of the result. I could handle everything except for the skeletons, which had been set up to carry five or so stick grenades. There really just wasn't any good way of dealing with those things, as they were effectively walking bombs. But man... That was some intense action.