That's good trivia. To good to ruin by cheating to answer.
this is exhausting to guess. I'm not including Game Show hosts or Talk shows which would alter this guess.
Confident:
Kelsey Grammar, Cheers, Frasier, The Simpsons
David Hassellhoff, Y&R, Knight Rider, and Baywatch
Jack Klugman, Odd Couple, Quincy, and the Greatest Gift (old time 50s show, I first saw surfing early during Covid)
Michael Landon: H2H, Bonanza, Little House
maybe
Tiffany Amber Theissen, Saved by the Bell, 90210, White Collar (not sure Bell or Collar hit 100)
Valerie Harper: MTM, Rhoda, and Valerie Harper show (think < 100)
short one way or another:
James Spader: Boston Legal, Blacklist, Practice didn't last long
Jimmy Smits: LA Law, NYPD Blue, and West Wing, no way he was on for 100 though
Cosby: I Spy (not sure if 100), Cosby Show and Electric Company
Sam Waterston: 4 bazillion Law and Order episodes!, Grace and Frankie has to be getting close to 100 it seems and I'll Fly Away (I think probably not 75)
Tony Danza: Taxi, Who's the Boss, Family Law (doubt it was 100)
Jeffrey Tambor: might have 4 30+, ThreesCompany/Ropers, Arrested Development and Larry Sanders Show, and that Showtime show he was on and played a trans.
Ted Knight: MTM, Too Close, he also had some spinoff variety show, noway it got to 100.
Ed Asner: MTM, Lou Grant, and I bet he's voiced about 1000 animated shows in aggregate.
Robert Stack: Untouchables, Unsolved Mysteries and I'm sure he's short on something else.
Danny Devito: Taxi, It's Always Sunny, I can't name a 3rd where he's had more than a cameo.