Maybe it's unfair to judge TNG by today's standards - in many ways, it was the first "modern-day" scifi drama. The shows that followed in its wake may have been better, but that's because they were standing on Next Generation's shoulders.
The show got off to an extremely shaky start with the weak 1st season. The 2nd season was a clear improvement, but it was not until #3 that the show really hit its stride. Each of the final 5 seasons had some classic, "must-see" episodes along with others that provided fun viewing.
The drawback is that nearly each of those 5 seasons had duds - particularly the final one, during which the writers shifted focus to DS9, Voyager, and the upcoming "Generations" movie.
In addition, the writers struggled with character development. With a few exceptions (Picard, Worf and to some degree Data), the characters "froze" in the 3rd season and never really developed. Those used to character- and arc-driven shows may be disappointed.
In addition, the show occasionally relied on alien-of-the-week plots, pseudo-scientific technobabble or preachy "message" shows. Some people like those characteristics; I do not.
Overall a very worthy viewing experience, and recommended. But I think that Deep Space Nine was overall a better show.