If we consider "jumping the shark" to mean an irreversable decline in quality, then TOS* is the only series that jumped the shark.
* Yes, I know I said I didn't think TOS jumped the shark, and that I like the third season --- it's even where I got my username from -- but I'll defer to general consensus for the sake of argument.
TNG suffered in the seventh season because TPTW had the mentality of "DS9! Voyager! TNG movies! Wait... we still have to finish TNG as a series? Oh.", but there were some great episodes in the seventh season and "All Good Things" was a nice note to end the series on.
DS9 had a condensed Final Chapter arc (it could've gone longer than 10 episodes) and an effective seventh season overall. No shark jumping or decline in quality towards the end.
VOY had a consistent quality during most of its run. It was mixed but it was a consistent mix. The seventh season also explored the Paris/Torres relationship better, dealt with civil rights (even if they were holograms) and dealt with issues relevant to 2000 (and today) such as the penal system, and especially health care. It was actually one of the better seasons, along with the fourth.
And ENT's fourth season was interesting, especially the Vulcan triology and duology with the human isolationists, the titles of those episodes escape me. But this is the exact opposite of a shark jump.