Who was the best showrunner (1987-2005)

[TMC]

• TNG Seasons 1-2: Gene Roddenberry
• TNG Seasons 3-5: Michael Piller
• TNG Seasons 6-7: Jeri Taylor
• DS9 Seasons 1-2: Michael Piller
• DS9 Seasons 3-7: Ira Steven Behr
• VOY Seasons 1-2: Michael Piller
• VOY Seasons 3-4: Jeri Taylor
• VOY Seasons 5-6: Brannon Braga
• VOY Season 7: Kenneth Biller
• ENT Seasons 1-3: Brannon Braga
• ENT Season 4: Manny Coto

If you want to be technical, I'm not sure that it's truly accurate to refer to any of them as "showrunners". This is because that term encompasses a lot of production responsibilities that Rick Berman has often shouldered even while not serving as head writer. In the case of someone like Berman, he may not have written episodes, but he certainly made decisions about what would air and ergo its tone and direction, so he'd be the showrunner for most of TNG.

And Gene Roddenberry as far as I know, was never the head writer on TNG. He was the executive producer, and very hands on during the first couple of seasons, but he never actually ran the writing room. Maurice Hurley was essentially the showrunner during Season 2 of TNG. Roddenberry was still actively involved in the show at that point, but had cut back his day-to-day involvement, and Michael Piller had not yet come on board.