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I dont think appearing for a few shows on the simpsons qualifies

there quite a few actors that have voiced on the simpsons

I made poor assumption that Sideshow Bob has been 100 episodes, took a guess on longevity of series.

Lucille Ball had three shows, I think they all went over 100.

Bob Newhart had three shows as well, but I don't think the one in the 90s lasted long.

I enjoy making the wild guess, mostly to learn how shocked how many/few episodes of a certain show there were in reality.

Dick Van Patten?  Eight is Enough, the Mama show from 50s, and I have no idea on a 3rd?

4 is a lot.  And with Coming To America 2 coming out, it's about to be 5.

I can think of several with two, and maybe a few with three.

You already mentioned Sly who has Rocky, Rambo, and Expendables.

Arnold has Conan, Terminator, and Expendables.

Mike Meyers has Austin Powers, Shrek, and Wayne's World.

right but just look at Eddie Murphy

Beverly Hills Cop
Sherk
Dr Dolittle
48 Hours

and now Coming to America

Like I said I think hes in 1st place

Craig T Nelson has to be in the all so close club:  Coach, District and Parenthood
While Andy Griffith might have two 200+ shows, not certain Matlock hit 200.
Raymond Burr with two big ones: Perry Mason and Ironside, doubt he had a 3rd hit.
Tony Shalhoub has a chance: Wings, Monk and I think he's lead in some regular show going on now.
Ted McGinley is in that Jeffrey Tambor area with a  lot of long material, not quite feature guy (Happy Days, Love Boat, Married w/, Hope and Faith, Dynasty)
speaking of Married w/ Children, Ed O'Neill with two solid runs (Family Matters)

Judd Hirsch: Taxi, Numbers and did Dear John make it to 100?

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.

Not sure is cartoons quality, but Bill Cosby also did the Fat Albert cartoon for years.

How many actors have been in 3 or more TV series that went over 100 episodes?  Can't be many.

I wonder about guys like Leslie Nielsen back in the 60s/70s he played a straight man/character actor on a lot of different shows.Mostly police/detective type series.Columbo,Streets of San Fransisco,The Wild,Wild West,Police Squad - 6 episodes.Sure there a many more but I would have to peek

Edit:curiosity got the best of me I peeked saw he appeared in KUNG FU - 4X,never would have guessed that