Now that last one I like Geronimo.
Right, this is going to sound odd but....A thought occured to me today. Alien snakes aside, the friends and foes of the human race as they are in 'Stargate' are basically humanoid, if not human. Therefore, appearances can be deciving/deceptive (am not sure which). You may see people as your friends, or at least not a threat, if they seem the same as you, but first impressions or appearance is little against what may exist underneath.
Another thing I think I've learnt is the importance of belief, and how real this can be. In 'Spirits' what were assumed to be the aspects of religion, turned out to be a very real danger. Also, it is the strength of belief that keeps the 'false gods' with such a following of Jaffa and so forth.
It has taught me to look further beyond what is there. OK, so I do that enough anyway, but I never thought that a series could be created which took genre of Sci-Fi in such a way that incorporated the basics of culture and ancient history. And that, btw, is a reason why I like 'Stargate'.