Star Trek: The Next Generation was an early 90's line from Playmates that arguably initiated the collectible action figure market with its collector-centric marketing strategy.
The Star Trek line had many shining "stars". Many different varieties of characters and aliens from the show were available, such as Esoqq (below). The figure sculpts had "cartoony" proportions and sculpts, giving them a fun, toy-like feel. Additionally, the Enterprise Bridge playset (above) is an incredible display piece, as well as an awesome toy, featuring lights, sound effects, and spring-loaded "sooshing" doors. No modern playset from Star Wars even comes close to its coolness!
Playmates expanded the Star Trek line to include the other series as well: The Original Series, Deep Space Nine, Voyager, and the movies (with the First Contact figures being the most detailed and realistic). The Star Trek property was popular for many years, but fell victim to 1) collector elitism (some figures were produced in such limited numbers that completism was virtually impossible for most collectors), 2) the degradation of the Star Trek franchise, and 3) overshadowing by the Star Wars juggernaut.
The Star Trek line is very much rejected by collectors at this point... which is great news for Star Trek fans as the prices for all the figures have plummeted. As a side note, if you buy carded figures and open them, they sometimes have an oily residue on the plastic. A few good washes with soap and water (along with an "airing out" phase) usually remedies the situation, but it may be easier just to buy loose figures. It makes you wonder what is really happening with the plastics when you keep figures carded for a few decades.