I suppose it is a bit unfair to suggest Star Trek as they were made so long ago, and I do remember enjoying them several decades ago.
Cat
I have seen Star Trek (the original series) for the first time in adult age and after having read almost all the best SF literature, so my opinion is quite different.
For the age in which the series was produced, and given that it was directed to a teen audience could go, but having seen it in the middle of the eighties, I wasn't particularly impressed.
The movie made in 1979 was quite good, but particularly in the end it resembles something more like 2001:A space Odissey then Star Trek. Another setting would have been better for this plot (but at the price of much less box receipts ).
I have also seen all the episodes of the following series produced, resisting only for a cultural reason because I found all very disappointing,
Last year, reading on a SF site an old interview with Charles Stross, estimated SF writer, I have discovered why.
See his site:
http://www.antipope.org/charlie/blog-static/2009/10/why_i_hate_star_trek.html