http://www.quora.com/History/What-is-the-most-epic-historical-battle-ever?share=1
Kind of interesting, none unexpected. Maybe worth a discussion?
These discussions are always a good time.
Back in 2002 I reviewed a book on another website that was entitled "50 Battles that Changed the World." Unfortunately, it appears that review is lost to time (though I may have a backup copy on a disk around here somewhere, today isn't going to be the day I unearth it).
Anyway, generally speaking any value-based list will have to be based on a series of assumptions. These assumptions will inevitably be where the meat and potatoes of debate will occur.
For instance, how does Cannae compare to any other battle? Let's say Desert Storm?
In the 50 battles book, the author notes that while Rome lost, it awoke the republic and set it upon its path to greatness. If we assume that Cannae did indeed spark the rise to Roman greatness, then any comparison to Desert Storm is probably invalid as America was arguably at the top of its game.
However, if we look at the tactical comparisons then the two are more comparable.
Nevertheless, these kinds of discussions provide excellent food for thought for guys like us.
I think I have that book, LB. If I do, it's buried in a box somewhere. And like your possible disk, today is not the day I am going to unearth it :) My vote? Meggido :)