You know, this thread kind of reminded me that not too long ago, I was mentally doing an inventory of who I thought the strongest actors in the series were and actually contrasting them, after a fashion, to DS9 and even to a lesser degree, to TNG.
I do tend to think evaluating series progression, Voyager tended to be a lot stronger of a series (as a whole) then TNG or DS9 and that's wholly because of the progression in writing and story telling. Sure, I'll be the first to admit, I thought the series suffered from the "little ship that could" syndrome while in premier, but re-watching the series as much as I have over the years, I've changed my tone a lot.
That being said, I do think Voyager suffers from having some of the weakest actors compared to the other four contemporary series.
DS9 had some real phenomenal actors in Avery Brooks, René Auberjonois, Colm Meaney, Armin Shimerman, Andrew Robinson and Marc Alaimo. Generally speaking, I think TPTB all but committed highway robbery with how often many of these actors appeared on the series and how much they were paid, but I don't have numbers to back that up (just a hunch).
On Voyager though, the only two outstanding actors we had were Robert Picardo (I might even argue he has been the best actor in all of Trek) and Jeri Ryan and I'd be heavily critical and say the only great actor in the series was Kate Mulgrew. I'd probably classify Robert McNeil, Roxann Dawson and Garrett Wang all into the "good" category.
I always hate, hate, hate to say this as much as Tim Russ currently does and has done to keep Trek alive, but his character just wasn't nearly as interesting as I felt it should have been. MAYBE it was a breakdown in writing, but Tuvok was always lacking.
Robert Beltran fell into that same category, his character had so much potential and just fell into a trend of nothing truly exciting happening. As a matter of fact, the episodes that tried to focus on his character ended up being some of the worst episodes in the series. His character and maybe him as a person has always been better at making other characters look good (Examples: "Life Signs" (S02E19), "Resolutions" (S02E25), "Human Error" (S07E18)).
Ethan Phillips character I think a lot of people might agree actually annoyed a lot of people but always felt so necessary. I ALWAYS disliked the character but always understood why he was here and would have loved to see them try something else for that 'spot'. I always felt like Pairs was just shy of being able to be the guy who coordinated supplies and it would have been fun to see Chell run the kitchen and keep him confined there. Heck, I almost think this would have given Robert McDucan's character a lot more room to grow.
Jennifer Lein? Well, as you can see above, there's three character I would have rather chopped or at the very least, would have rather seen dropped back to "part timers". I would have been fine with Tuvok, Chakotay or even Nelix only being on screen when they needed to be instead of making up reasons for them to be on screen, because frankly, Jennifer Lein's character was a lot more compelling then any of theirs throughout the entire series.