You could probably classify bad hosts into five categories:
Johnny Paycheck - the hosts who are only there to pay the bills, and it shows in the lack of enthusiasm in their work. Examples: Louie Anderson, Jack Gallagher, Patrick Duffy, Jimmy Kimmel
Tries Too Hard - the ones who pretend to be a game show host instead of hosting a game show, exuding all the cheesy caricatures of a host. Examples: Patrick Wayne, Chris Wylde, Donny Osmond, about 80% of the hosts of kids shows
Technically Unsound - the people who just don't have the chops to run a game smoothly. Examples: Jim Caldwell, Michael Carrington, Jim Lange (take him out of The Dating Game and he flounders)
Stiffs - no engaging personality whatsoever. Examples: Ron Maestri, Joe Farago, Mike Reilly, Ty Treadway
Guilty by Association - the show's bad, so the host has no opportunity to be anything other than bad as well. Examples: Roger Lodge, Kirk Fogg (once Olmec took over all the game explanations), Rossi Morreale, Corbin Bernsen