Vanilla:
Most DPS Shaman ran a tri-spec build, more or less like this. Open with Elemental Mastery + Chain Lightning (Lightning Bolt vs. a single target), spam shocks, pray for Windfury procs and use a huge, slow two-hander. This was called the "suicide shaman" build. It was pretty awful in raids but great at PVP, especially before the axe from Scarlet Monastery got nerfed (infinite self-procs were hilarious). It wasn't really Elemental at all, but most of your points went into the Elemental tree.
True "Elemental" Shaman just spammed Lightning Bolt.
Burning Crusade: Again, spam Lightning Bolt, with the occasional Chain Lightning thrown in. I only played my Shaman as Resto during BC, but I think there was one raid tier where it was a good idea to work in shocks.
WOTLK: Flame Shock, Lava Burst, Lightning Bolt. In some patches (3.2-3.3) it was good to work in the occasional Chain Lightning, even against single targets. Emphasis on Haste break points.
Cataclysm: Basically same as now.
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Agreed. We found exactly one meaningful use for earthquake, ever: Pre-casting right before Valks on H LK. At the time, Earthquake wasn't on the stun DR table, which could mean the difference between your bads blowing up the Valkyr and you dropping to your death.