I was never a Star Trek fan. I thought the original series was cheesy. I hated William Shatner and thought he was a complete joke fucking every species of woman he came across.
But after the first season or so of TNG, I got hooked. I didn't see it as cheesy or cornball at all. I thought it was very clever the way they handled many present-day socio-political issues in the guise of a storyline. As well as some deeply philosophical ones too.
I thought it was clever and funny, and I immediately liked the characters of Captain Picard, Data, and Warf. The rest were so-so.
I tried keeping my interest in the Trek series to follow, but I abandoned DS9, Voyager and Enterprise in less than 3 shows.
I tried getting back into Voyager when 7 of 9 was introduced. However, I only turned in for her tits, and tuned out when I got an eyeful.
To me, the quality of a series is in the ability of the leader to carry the story, and the crew. Patrick Steward was a very strong leader. Cptn. Janeway was crappy, and I don't even know the rest of the Captain from the newer series.
My vote goes to TNG. Not only was the series phenomenal, but they were the only crew that could successful carry the torch on the big screen. (I hated that they killed Data in the last movie).