Sci Fi wasn't exactly a new thing in 66. Serious Sci Fi maybe, but even that is debatable, Forbidden Planet & even Twilite Zone & the odd 50's Sci fi movie could well be considered serious Sci Fi. However, it WAS perhaps the 1st serious Sci Fi tv show. That would be in my top 4. Not neccessarily in this order, I'd go with this.. 1. Serious Sci fi, ( interesting futuristic technology & humanistic drama, instead of just monsters & green men). 2. Metaphysical & Far out type ideas were just coming into vogue 66-67. Timing was pretty good. Age of Aquarius, Flower Power era. 3. Great cutting egde special effects, combined with awesome designwork, Enterprise in particular. Before that it was mostly rocket looking spacships. 4. Last but not least good stories nailed by great actors. It seems to work for any age group, which cannot be said for many other shows of the same timeframe.