Nicholas Meyer did a fantastic job with Wrath Of Kahn considering they had little to no budget. He also had a wonderful and paced perfectly script. I thought he did a good job with Undiscovered Country, although I didn't think the story was as strong as Wrath of Kahn. Jonathan Frakes was great with First Contact and give the subpar script for Insurrection, I think he did the best he could with it.
Stuart Baird should never be let near another Star Trek film again. He is an excellent editor but an average director. (although I loved U.S. Marshals) J.J. Abrams does a good job and would be one of my favorites if it weren't for all the lens flares and camera shaking for space battles. I like to see the battles not have to take Dramamine to watch them.