Obviously, this is a weighted question. If you look at it from a completely business standpoint, the winner is Cronin by a longshot. His originals and direction in which he moved the network, while we won't know the full repercussions of this shift in programming for a while, have taken the network and moved it, according to ratings posted in another post, almost consistently in the top-40.
I like the side-by-side comparison that Seth made; I think he covered most everything, both good and bad, that both did. If I let the classic game show nut speak, then I'd probably say the Fleming era was better because I don't think we'll ever see shows like "Bumper Stumpers," "Go!," "Chain Reaction," etc. on the regular schedule again. However, look at what Cronin gave us: Marshall HS, LMAD, and, of course, PYL, the most sought-after package of reruns by most casual game show watchers. While I can take or leave LC, it's no worse than Burt Luddin or AN3AC.
This has to be one of the toughest questions posed because Cronin is certainly the winner via business, but Fleming wins if we consider who devoted more of the schedule to the classic game show nut like us (!).
Nevertheless, I would find it almost unbelievable if GSN were still in existence today if Fleming were still at the helm; now, most everybody knows what GSN is as opposed to the response, "There's a network like that? Who knew?"
In summary, I pick Cronin. Despite the fact that I got to see way more classics in the Fleming era, Cronin's direction will keep GSN going for quite a while, and who's to say what the future will hold? Hopefully, we can stuff the ballot box and make them dust some stuff off for the FOF, if they do it again this year!
Anthony