Short answer: none. They all have life in them. It's the larger narratives that are the problem. Fix the big arcs, and the plot devices will feel fresh again.

I'd never watched more than a glimpse or two of Star Trek until last year. Binged for a few weeks last winter for some remedial pop culture education on all the series except TOS and Enterprise, neither of which I could stand.

None of it grabbed me enough that I'd ever be a trekkie, but I liked Voyager the best. It has a legitimate series arc and genuine sense of background spatial and temporal vastness I like in my space operas. Space is really so big/long-term that it seems like a crime to not have drama on the scale of decades at least.

The other franchises are far too monster-of-the-week for my taste. That, rather than plot devices seem to me to be the fertility problem. I'd happily accept all the hackneyed plot devices if they were used in the context of a new big-arc narrative.

But I can't think of any good Voyager-scale arcs.