Voyager is one show I can come back to time-and-again. The closest show to the heart of Star Trek IMO is Eureka, its just fun, you can't take it too seriously but its got the sense of "3 year olds looking under rocks and discovering aspatialdiscontinuity" that some of the best episodes in all the ST series. And then there's Fringe... but that's SciFan more than SciFi.
What I can't get over is that we see so many banal murder shows popping up, they can recreate death over and over, yet the idea of playing with a whole universe of multiple realities they find limiting? Whatever. Sure, I agree that any new series would have to take a radical approach, for my money a variation on Asimov's Foundation series? That was based on a single species, but I like the more psychological tail twisting that went into that. Or steal Lazarus Long from Heinlein! Ursula Le Guin's Hain universe... Mmm, I do like old SciFi....
Even something based in the ST universe, but single planet orientated - maybe zip back to one of the border planets the Marquis were based off, or that Delta quadrant planet the '37s were taken to (remember, random Amelia Earhart ref?). I even just finished re-watching the Voyager ep where the "Demon" class planet that copied people. Or the Voth, or Seska's son... That is one of the things I love about Voyager still: the rippling wake of change and effect they left behind them, infinite other threads to pick up on.
The longer the networks leave it between Star Trek series the less in-built fan base they will have to build on. I think the iron is starting to get mighty cold.