Licensed tabletop RPGS are REALLY hard to get right. Most of them are blatant cash grabs done to make money while the getting his good. Some game companies did it right. (West End Games had more or less the same engine for most of their movie license games. Hence, with only minor rule mods you can easily do an Indiana Jones/Ghostbusters/Men In Black crossover. Don't ask how I know this.)
Last Unicorn's brief stint with Star Trek was great. I only own the base book for DS9 because the rules are pretty much the same for TOS, TNG and DS9. It didn't just choose DS9 beause of the three series they made, it was my favorite. It was because you get ALL the playable species templates from TOS and TNG and most of the ship stat blocks. At the time I bought it, getting the Worlds of The Federation was cheaper than buying the TNG book and getting the TOS narrator's tool kit got me all the missing TOS stuff I wanted.
The game is fun. Really, the only complaint I have is one that I think might turn off someone more used to D and D. In theory, with D and D you can role your stats, chose your character species, class, etc. in a matter of minutes and have a very personalized character in maybe 30-45 minutes. If you're starting at a command level game (as most GMs do) you need at least a whole session. The other problem is that because a command level game wouldn't have two security chiefs, it is best for the whole party to be together when they are making characters. Otherwise, you wind up with someone playing a position they don't want. The first time I played, I got to the table late. So I had to be security or tactical by default.
The reason I haven't invested in any Trek game since is I feel Last Unicorn nailed the feeling of Star Trek so well that there isn't much need for it. I mean, apart from the new game covering Kelpians there isn't much else I would want. Give me 2 hours and some scratch paper, I can make a species template for them. (Just as I did for Denobulans, Male and Female Orions based on what we learned on Enterprise, and the 'augmented Klingons'. (Where I was lazy and tweaked the fitness score a bit, raised the intelligence and call it a day.)