Well naturally: Jim Henson was a LEGEND as far as the art form of puppetry is concerned, and sure people are going to come along and try to duplicate what he did, because that's natural in television, particularly with particular series like Bewitched Vs. I Dream of Jeannie, M*A*S*H Vs. Hogan's Heroes, Trading Spouses: Meet Your New Mommy Vs. Wifeswap, Nanny 911 Vs. Supernanny, etc, etc, etc. It all depends, mostly, on what material people have to work with, and how well of a performance they give off, and if they're lucky, that might be ALMOST as good as the muppets, but naturally, they never will be.
Why wouldn't you be as good? Someone mentioned the Beatles earlier, and they, along with Henson, Elvis, and a bunch of others, have been elevated to this position where people think there will never be anyone better. That's silly. People get better over time; successive generations learn from what was accomplished before, and do better. Culture and the arts is a progression. It's like science: while many would point to Einstein as the pinnacle of a scientific mind, Hawking has, by all rights, equalled or bested him in many regards.
We only say that Henson is the best ever because of nostalgic reasons: he was the first "Best" that we ever saw, and so must remain that way forever. Now, I'm not suggesting he wasn't good, wasn't great, and that few people approach his levels, but the very idea that the art peaked several decades ago? That's crazy.
What makes the Muppets perfect? The design of the puppets? There are designers out there who make puppets that are arguably better looking, or more sophisticated technically. Is it the performances? Again, there are people who do it as well or better. Is it because they were "first?" They weren't, of course, even though the common view seems to be that Henson practically invented puppeteering.
And what does it mean when you say Muppets, anyway? Henson specifically? While he built the initial puppets from the 1950s Public Access show and his TV commercials, he hired a puppet builder, and quickly got puppet designers, and he had a staff of writers to help him. "Jim Henson" was an idea man of great quality, no doubt, but he was far from a solitary genius. And these days, it's not like the Muppets have Henson doing any of the designing or writing, so what, today, does "Muppets" even mean? I'm assuming Muppets is shorthand for the Muppet Show period, but that's a shorthand for a sensibility, and those are as subjective as you can get.
I'm not meaning to sound negative of anybody in the forum, nor of Henson specifically; though I'm not a life-long devotee of the man, when I got into puppetry, I did so chiefly through the Henson Company's work, and I have a tremendous amount of respect for the craft and the creative. But I wouldn't be so naive or so adulating to think that the best has already happened. In all creative endeavors, there are those who set the direction for a long while, inspiring floods of imitators, most of whom are pale at best, but there are, there always are, those who find ways to elevate what came before, to amplify and transcend it in ways that the earlier trendsetters couldn't have imagined, and those people come to set the new direction. That's the way art goes. It's the way culture goes. The way science and politics and everything goes. It's the way life goes.
You should never take it as writ that this person or that person has done it as well as anyone will ever be able to; that's just fanboy talk, and it will limit what you achieve, because it will limit your attempts. I have lots to learn, lots to improve upon in what I do, but I would never for a moment think that I'm toiling in what is by that logic a dead industry, trying to match up to some ever-present perfection. If I was, what would be the point?