Jason Bateman
Silver Spoons - 5 seasons
The Hogan Family - 6 seasons
Arrested Development - 5 seasons, kinda
The Ozarks - 2 seasons so far
James Garner had Maverick, Rockford Files and Eight Simple Rules. There were several variation on Maverick. He also had Nichols which was short lived.
Peter Krause has gotten pretty good being first or second-billed in the following:
Parenthood - 6 seasons
Six feet Under - 5 seasons
9-1-1 - 3 seasons and counting
Plus:
Sports Night - 2 seasons
Dirty Sexy Money - 2 seasons
The Catch - 2 seasons
He’s probably not the winner, but the first guy that leaped to mind was David Duchovny.
X-Files, Californication & Red Shoe Diaries and he’s unquestionably the lead in those non-ensemble style shows.
BTW, I think it’s cheating to use people that are on ensemble shows, but admittedly that’s a blurry line. I suspect that Courtney Cox was the “lead” of Friends when it premiered, but in reality all 6 main characters were either the lead or none of them were. Similar argument could be made for 90210, the plethora of procedurals like Law & Order, ER, CSI:Whatever and prime-time soaps like Dynasty and Melrose Place. SNL and other sketch shows suffer from this perhaps even worse. Even Seinfeld, if not for the title and Jerry’s position as writer/producer, could be considered to have 3 “leads”.
Mark Harmon has had leading roles in Flamingo Road, St Elsewhere, Chicago Hope and NCIS. Incidentally it was only with NCIS and the internet that I recognised him as the guy I’d fancied in every one of those roles 
Tim Daly
[ul]
[li]Wings - 8 seasons[/li][li]Superman: The Animated Series - 3 seasons[/li][li]Private Practice - 5 seasons[/li][li]Madame Secretary - 6 seasons[/li][/ul]
Kate Jackson :
Dark Shadows
Rookies
Charlie’s Angels
Scarecrow and Mrs. King
She was only on that show for a year, and she wasn’t a star.
Building off this we have Bruce Boxleitner
[ul]
[li]How the West was Won - 3 seasons[/li][li]Scarecrow and Mrs King - 4 seasons[/li][li]Babalon 5 - 4 seasons[/li][/ul]
He also had a major role in something called Cedar Cove for 3 seasons, but it looks like he was a supporting cast member.
James Arness was the top-billed star in Gunsmoke for 20 years.
Yes, but he only starred in one successful series.
If you look at the CSI box sets, Danson is the most prominently featured on the cover of three of the four seasons he was in.
Kristen Bell arguably has 4: Veronica Mars, Gossip Girl, House of Lies, and The Good Place.
She wasn’t top billed in Gossip Girl. In fact, she wasn’t even credited. But she was the titular character and in every episode!
Maura Tierney
[ul]
[li]News Radio - 5 seasons[/li][li]ER - 10 seasons[/li][li]The Affair - 5 seasons[/li][/ul]
How the West was Won ran for 3 seasons.
I stand corrected.
Eric McCormack
[ul]
[li]Will & Grace - 11 seasons[/li][li]Travelers - 3 seasons[/li][li]Perception - 3 seasons[/li][li]Pound Puppies - 3 seasons (voice)[/li][/ul]
Seth MacFarlane
[ul]
[li]The Orville - 3 seasons[/li][li]American Dad! - 15 seasons (voice)[/li][li]Family Guy - 18 seasons (voice)[/li][li]The Cleveland Show - 4 seasons (voice)[/li][/ul]
He’s not really a star in The Cleveland Show, so it probably shouldn’t be listed. But he’s also credited as the creator of all 4 shows, which is unique.
Seth MacFarlane made me realize I should look at Mel Blanc’s imdb page. It’s… extensive. 1149 acting credits.
Looks like he was a lead voice actor in
Heathcliff and the Catillac Cats
Captain Caveman and the Teen Angels
The Bugs Bunny Show
The Flintstones
If he had lived at a different time, he might have had dozens of successful 3-year shows. As it is, most of his credits are for single animated shorts, and most of the shows lasted only 2 seasons, not 3.
Here’s a thread I started on a similar subject, but with slightly different qualifications. I didn’t require a starring role, and the cutoff was 80 episodes in at least three different series. See especially the posts by obfusciatrist who took over as official record-keeper of the thread. That was almost 20 years ago, and some actors have gone on to star in more seasons of shows since then. The last updated official list from that thread included the following actors:
Denise Alexander
Richard Dean Anderson
Rene Auberjonois
Barbara Babcock
Lucille Ball
Bea Benaderet
Barbara Berjer
Casey Casem
Tim Conway
Bill Cosby
David Coulier
Jane Curtin
Abby Dalton
William Daniels
Shelley Fabares
John Forsythe
Peter Graves
Phil Hartman
David Hasselhoff
Bernie Kopell
Don Knotts
Michael Landon
Heather Locklear
Judi Evans Luciano
Lee Majors
Wendie Malick
Howie Mandel
Gavin McCloud
Alvin Melvin
Martin Milner
Harry Morgan
Lorenzo Music
Tom Poston
Burt Reynolds
Dolph Sweet
Frank Welker
And the following were listed as questionable
Don Adams
Bill Bixby
Tom Bosley
Julie Kavner
William Shatner
Dick Van Dyke
Betty White