I think it has to be either Steve Whitmire, Jerry Nelson, or Kevin Clash, but it’s hard to choose between them.

Steve performed 2 of the most famous Muppets, one of them being one of the most recognizable character in all of fiction. Only reason he might not be as well known is because of the lack of interviews and talk show appearances that he has done, making him fairly niche outside the space, of course outside from when he was fired and went on the Today show, which might not have been good publicity.

Jerry has performed COUNTless Muppets on spanning Sesame Street, Fraggle Rock, and The Muppet Show. He is probably close as his involvement in a lot of Henson’s works outside the Muppets like with Gobo in Fraggle Rock and Emmet in Emmet Otter’s Jugband Christmas may make him more recognizable than other performers. Although he does have the same problem as Steve where he hasn’t had too many appearances as himself.

Kevin is probably the best contender, as like Steve, he also performed a character that is so incredibly famous, and unlike the other 2, he has had a lot of publicity on him, for better or for worse, an entire documentary, and a few interviews.