Particle Of The Week (Voyager) had its moments, but for me, you can't beat TNG. It really got going from mid season 2 IMO, and got better and better throughout. NexGen effectively validates the genius of the original idea, because it was, from launch, a continuation of it. The flaws in DS9 (too static) Voyager (too isolated ... exactly how many shuttles does an Intrepid class starship carry?) and Enterprise (not enough tech, especially in the early seasons. Transporters were an inspired idea in the original series, for good reasons) are all, to a greater or lesser extent, caused by deviating from one or more of the plot devices that made TOS and TNG so flexible.
Having said that, I've watched every episode of every series, often several times over, so they're not all that bad.
