Croc could possibly smother Ace's flames, but it depends on how you want to treat Ace's flames. If you treat their orange-red nature as indicative of the heat that they'd have in the real world then Croc would win. If you are the sort of person who just goes "The flame's really hot" then he might glass Croc.
As for the actual point, lightning and flame have no conductivity or resistance, unlike metal/wood/pretty much any solid substance. They'd really do jack all to each other, I suspect. Although, Ace's heat is probably a far more constant source than Enel's lightning, so it's possible he could simply wear Enel down through that alone (Enel wouldn't really be used to high temperatures living so high up and chillin' in the clouds). That's about the only way I can think that either would win.
Yeah, I never believed in the "greater heat beats lesser heat" thing, it's ridiculous. If you hit a fire with lightning in real life, would the fire stop? No, of course not.
While we're on the topic of Logia-type Fruit, what "forces of nature" are really left to be encompassed? We've covered lightning, landslides, ice age, wildfire, drought, volcanoes, choking smoke[pyroclastic flow?] and the twinned cosmic threats of heatwave & gravity/pressure. I can only think of a handful of forces left:
Floods (Water, obviously)
Storms (Wind)
Cave Collapses/Earthquakes (I'd imagine some form of gravel Logia, though this sort of matches with the landslide/mud logia theory I'm on)
Epidemic (Some form of spore or bacteria, but I doubt this logia for simply being too similar to Magellan's DF)
Impact Event (meteorites, though this would again be very close to an existing fruit, this time Akainu's)
Possibly some obscure ones like Limnic Eruption (CO2 FTW), or Reclamation (over time plants will ruin just about any manmade structure, so whilst not obvious to a regular view point plant growth could be seen as a force of nature).
Are there any other real forces of nature worth mentioning that aren't a combination of the above somehow? With the hierarchy thing I could see Snow representing blizzards as a weaker form of the Ice logia, but then it'd be odd to introduce the weaker one later.