Am I the only person who noticed that the Roman's did not use phalanxes?
Well, aside from the early republican army, but I challenge anybody to seriously claim that that is Rome at it's greatest power.
Anyways, the Roman legionary system did a pretty decent job of countering elephants when they encountered them (Pyrrhus's expedition, for instance).
Finally, I would point out that the wars of the successors saw elephants used fairly frequently, and it did not render the Macedonian-style phalanx obsolete (it declined in importance, but not because of the presence of elephants).
Yeah they declined in importance because of the legion's ability to operate in small units. In many battles the tactical flexibility of the legion beat the the weight of the phalanx. And as many people pointed out, Romans faced elephants not just with Pyrrhus but also against the Carthaginians (who used African Elephants) and beat them handily. Elephants were mobile tanks (moving at roughly the same speed on the ancient battle field that the first tanks did on the modern battlefields of WW1) that were hard to control and really only good as terror weapons and as archery platforms. Hands down I give this one to the Romans.