earth (and void) is a great general purpose flare. there's a lot of random stuff immune to fire or cold, little is immune to getting brained by a rock.
the reverse of that, of course, is not much is WEAK to earth flares. Versus fire or ice have a collection of things that it works great against (trolls obviously being the big one with fire), you also get icemule hunting in general there.
I lean towards fire for that reason. You pretty much always have a troll around your level that you end up hunting, all the ice things in icemule / the glacier in TI, GoS warcamps, etc. But if for whatever reason you don't see yourself doing any of that regularly, i'm +1 for earth as well.
Mithrilschlong, 2015-03-10 to slightly later on 2015-03-10. You will not be forgotten!
usable Meteor Swarm, late 2020-12-30 to early 2020-12-31. You will also not be forgotten!