I believe you've developed a fondness for Stewart's portrayal of Picard. Stewart displays experience, charisma, aged persona, and a very 80s style of leadership. Who wouldn't want Picard to be your boss? He's able to solve real problems, and commands with excellence. Stewart played him like a fine wine. Really all of the ingredients were ripe, which is why you may get the feeling of "role of his career". In the series, the writing was typically spot on as well as the direction and his approach to the character. Later, the only thing that saved the movies was his ability to read lines.
Shatner's portrayal of Kirk is probably next to best, especially in the movies. You have to forgive the nature of how they shot the show in the 60's. Often times the scripts were delivered so late Shatner was unable to memorize his lines, which reportedly created "The...Shat...As..We Know It!"
I actually thought Brooks really developed with his character throughout the duration of DS9. Some call it over the top, some say over acting, but I've always been fond of Ben Sisko. I'm not sure any other actor could have done as good of a job in this role. The only thing I cringe at is that "Wow" moment in the pilot on the beach with Jennifer.
If you can get past Mulgrew's voice you'll love the Janeway. I think Mulgrew single handily saved this series. She's a class act.
I've always been a huge fan of Bakula. I was so excited when Enterprise was announced with him at the helm. I think that's the reason I hung on to this show for so long. Honestly though, I blame the weak episodes and writers that made his character so wishy washy. Season 4 was a vast improvement for Archer.