Mine's gonna have some hot takes in it, so get ready.
(Note: I'm choosing not to rank Al Roker because 1: I haven't seen enough of his work, and 2: IIRC he only hosted with celebrities, never civilians.
1. Steve Harvey - Say whatever you will about the current product. Steve took a show that was not even on its last leg, but on its ass, and brought it back to the #1 spot, beating Wheel of Fortune for the first time in almost thirty years. He also took the format international, hosting the South African version.
Sure you could say that YouTube and the raunchy contestant answers had a lot to do with it, but give those same answers to Karn or O'Hurley, and they go nowhere.
2. Ray Combs - Ray Combs did something Richard Dawson never had to do, which was navigate the show through major format changes. Even when the show started to become almost unrecognizable, Combs conducted the proceedings beautifully. I think the way Combs was unceremoniously shown the door was tragic.
3. Richard Dawson - Being the OG always lends itself to a positive bias, but let's face it. He was in the right place at the right time. He did a great job, don't get me wrong, but this format probably would have gone to #1 at that time with just about anyone with any sort of comedic timing at the helm. Probably not Joe Namath.
(Note I said "at that time." Don't be pointing to later hosts as a counterexample.)
4. Richard Karn - Richard Karn basically went the whole show as a traffic cop. If anything particularly great happened, it wasn't because he made it happen.
5. John O'Hurley - Same exact critique as Richard Karn, but O'Hurley seemed to be playing a caricature of a game show host. He also left the show because he felt the questions were getting too risque, which we later found out would be part of the formula for the show's renewed success.
6. Louie Anderson - I'd really like to rank Season 1 Louie and Season 2 Louie separately. I'd rank Season 1 Louie above Karn, but by Season 2, it got to the point where you could just see that Louie would rather be anywhere else.