We've occasionally discussed game shows that have aired on the "Big 3" networks (off the top of my head, I don't think any shows have aired on ABC, CBS, NBC, and FOX*), but how about hosts who appeared on the Big 3?
-Bill Cullen: TPiR on ABC and NBC, Three on a Match, Hot Potato on NBC, Child's Play on CBS
-Peter Tomarken: Bargain Hunters on ABC, PYL on CBS, Hit Man on NBC
-Bob Eubanks: Newlywed Game, Trivia Trap on ABC, Card Sharks on CBS, Dream House on NBC
-Monty Hall: LMAD on ABC, Video Village on CBS?, LMAD, It's Anybody's Guess on NBC
-Tom Kennedy: You Don't Say! on ABC, Body Language on CBS, Password Plus, Wordplay on NBC
-Allen Ludden: Password (Plus) on all three
That's just a few I recall...obviously it's not the hosts' entire resume, just enough to fit all three networks
*/Unless Big Deal counts as part of the LMAD franchise