The list of actors who have gone from Marvel to DC (and vice versa) is quite extensive
Oh there's more. Lots more.
From one Marvel property to another
Rebecca Romijin…Mystique (X-Men) to Joan (The Punisher)
Jon Favreau…Foggy Nelson (Daredevil) to Happy Hogan (Iron Man)
Chris Evans…Johnny Storm (Fantastic Four) to Steve Rogers (Captain America)
Ray Wise…Secretary of State (X-Men First Class) to Hugh Jones (Agent Carter)
Ben Foster…Dave (The Punisher) to Warren Worthington (X-Men)
Gemma Chan was in both Captain Marvel (Minn-Erva) and Eternals (Sersi). Michelle Yeoh cameo'd in GoTG2 (Aleta) before showing up again in Shang-Chi (Ying-Nan).
From DC to Marvel
Michael Keaton…Batman (Batman) to Vulture (Spider-Man Homecoming)
Tommy Lee Jones…Two-Face (Batman Forever) to Col. Phillips (Captain America)
Ryan Reynolds…Hal Jordan (Green Lantern) to Wade Wilson (Deadpool)
Angela Bassett...Amanda Waller (Green Lantern) to Ramonda (Black Panther)
Tom Hardy…Bane (Dark Knight Rises) to Eddie Brock (Venom)
Michelle Pfeiffer…Catwoman (Batman Returns) to Janet (Ant Man & Wasp)
Laurence Fishburne…Perry White (Man of Steel) to Dr. Foster (Ant Man & Wasp)
Clancy Brown…Lex Luthor (Superman) to Maj. Schoonover (Daredevil)
Okay, about Clancy Brown...
First just in the movies, he lent his voice to two eldritch monsters: Green Lantern (Parralax), then Thor: Ragnarok (Surtur).
If you're going to count TV, that's a whole ocean of extra crossovers, but just looking at Brown; for animation, if you're counting Lex, you also gotta count Avengers: EMH (Odin) and Ultimate Spider-Man (General Ross & Taskmaster). And if you're counting live-action TV, then you also gotta count Flash (General Eiling).
Oh yeah, and then there's Jared Leto (Joker & Morbius.)
From Marvel to DC
JK Simmons…J Jonah Jameson (Spider-Man) to Commissioner Gordon (Justice League)
Willem Dafoe…Norman Osborn (Spider-Man) to Vulko (Aquaman)
Idris Elba…Heimdall (Thor) to Bloodsport (Suicide Squad)
Ben Affleck…Daredevil (Daredevil) to Batman (Batman v Superman)
Zachary Levi…Fandral (Thor) to Shazam (Shazam!)
James Marsden…Cyclops (X-Men) to Richard White (Superman Returns)
Michael Clarke Duncan…Wilson Fisk (Daredevil) to Killiwog (Green Lantern)
Taika Waitit pulled of the rare DC-Marvel-DC trip, appearing first in Green Lantern (Tom), then in the Thor movies (Korg), then cameo'd in Suicide Squad (Ratchatcher).
Randall Park showed up in Ant Man and the Wasp (Jimmy Woo) then in Aquaman (Dr. Shin).
Running opposite Michael Keaton is Dolph Lundgren, first with Punisher in '89, then in Aquaman (King Nereus) in '18.