What can we say about Start Trek that hasn't been said already? Probably not much! The series was a trailblazer, paving the way for many of other space travel shows and several very successful spin off series (affectionately known as TNG, Star Trek Voyager, Deep Space Nine, Enterprise, etc.).
The charm and appeal of the series lies not in its story lines or special effects, but in its characters. Kirk and Spoke have become cultural icons in our generation. And who hasn't heard the phrase "Beam me up, Scotty." Add to this the interaction between the characters (the friendly bantering of Spoke and Dr. McCoy, for example) and you have a great show.
I have the entire series on DVD and enjoy watching it to this day. A true classic!