Well, I like Festus just fine, it's just that I like Chester better.
I wonder if it just depends on who you grew up with? Chester was in the earlier episodes, which are rarely shown in reruns, so he's just not that familiar to me. Gunsmoke went off the air when I was around 5, so I don't remember much about it, except I'm thinking it came on Monday nights at 8. I do vaguely remember my parents letting me watch the opening credits, but then I had to go to bed.
But, I've seen Gunsmoke tons of times, in reruns. They've almost always been the Festus episodes. I've seen a Chester episode every once in awhile, and I guess I just got so used to Festus, Chester just doesn't feel "right" somehow!
Similarly, I know a lot of people hate the Darrin #2 in "Bewitched". But, that show went off the air when I was 2, so I only really know it from endless reruns. For the longest time they only showed the color episodes, which meant that Dick York and Dick Sargent got equal screen time for me. I've just come to accept the two Darrins as a fact of life, and like them both in their own way. They replaced Aunt Clara with Esmerelda around the same time. I think most people prefer Aunt Clara, but again, I like them both.
I didn't see a black and white episode of "Bewitched" until I was in my early 20s, so to me, Sandra Gould was the "real" Mrs. Kravitz. Although oddly, I saw her on a B&W ep of Jeannie this morning, in a bit role as Tony's housekeeper! I prefer Sandra Gould to Alice Pearce when it comes to Mrs. Kravitz, but to me, I think it's just because that's who I grew up with.
One minor character change that I really don't like though, is the guy who played Darrin's father. I'm too lazy to look up the actors' names, but in most cases he was played by the guy who was the president of the CF&W Railroad on "Petticoat Junction," Norman Curtis. On "Bewitched" I thought he was a likeable guy. Distinguished, level-headed, and pretty good at putting up with his wife when she pulled one of those "FRANK, I have a sick headache!" moments. But, a couple times they slipped in another guy to play the Darrin's father, and he seemed, well, kind of goofy.