TNG had run it's course by the end of the 7th year it was no where near the heights of S3-5. In contrast DSN which to be clear is ST (the OP might not like it, but that doesn't mean it's not ST) managed to maintaina higher standard of episodes in it's last year. That isn't to say it didn't have weaker episodes in that year, it's just that comparing S7 of both shows I would have to give DSN the award for being most consistant in terms of quality.
^and I agree Stewart played the role of Professor X well, with the material he had to work with.
What helped DS9 was them switching over to story-arcs. Look at the first couple of seasons, where it was more or less TNG on a space-station, once they had a defined goal and story that was all DS9's alone the show got better.
Oh I agree, though I think arc based shows such as DSN and B5 came out a couple of years too early for when that sort of stroy telling became popular.
Perhaps after 15 or so years with arc based shows being more popular we are moving back to a period where more episodic shows are prefered. Like with many things it's striking the balance between the two.