If you want play to play it online nowadays either play over Hamachi with some Bros or use Voobly. Getting this with the expansion is recommended. More detail, more customization, pretty much awesome all around, as long as you're into the RTS genre. AOE III takes over from here, but it just doesn't have the charm of the first two.
The sequel takes you through the next 500 (actually, 1000 - from the fall of Rome, which was the 5th century CE, to about the fall of Constantinople, or 1453 CE) years or so, from the decline of the Roman civilization to the invention of guns.