Nostalgia can play a part at times. To a certain extent our tastes in music/film etc... are definied during our youth. People complain about modern music/films/TV shows etc.. not being as good as it was when they were younger. But of course it would be true to say "No matter the era there is some good and some dire stuff".
Did I grow up on Trek, sure I did I remeber watching it on BBC2 in the 80's when I was a wee nipper, along with other TV shows from that era "The Man from U.N.C.L.E.", "Mission Impossible", the Gerry Anderson shows "Thunderbirds", "Captain Scarletand the Mysterions" etc..
But of course the TV landscape has changed a lot in that time. I remember when we only had 3 TV stations in the UK. But today with hundreds of channels, OnDemand services etc.. Just about everyone is catered for.
Star Trek has withstood the test of time. Is it because of production values, FX, acting etc.. Perhaps that has played a part, but I would say it has stood the test of time because of the stories it told. The best FX in the world can not compensate for the lack of a good story, a good story however can compensate for lacklustre FX.