LordXenophon played Empire Earth

Dunno how that would work considering most games like to make the lower tiers inferior in almost everyway so if you are a couple of teirs under you are screwed.

The time travvelers don't attack or build. They mostly just stand there and defend the time machine. That gives you plenty of time to build up your civilization, defeat or convert your neighbors and prepare for the assault on the time traveller compound. There's plenty of resources on the map and you are allowed to unlock every unit and upgrade in the game, even ones that don't make sense for you to have. If you concentrate on building and keep your army to a minimum for a few minutes, you can quickly reach the same teir as your strongest neighbor.

Just be careful with scouts, fishing boats and aircraft, because one or two of their units will sometimes follow you back to town. I used a few impasse lines here and there, but never for the time travellers. They can follow you anywhere.

During my last playtest, I tried building an airfield a short distance from their compound so I could swarm them with bombers and gound attack fighters. Just a few minutes after the air raid began, my airfield was mobbed by battlemechs. I was trying to test their defenses against airstrikes, but this was not what I had in mind. Even so, while the mechs were destroying the airfield, I had a citizen build a wall around them and isolate them from their base.

What's the lowest epoch you have to advance to before you have a chance to win?

I haven't really been trying to test that. I've also been making it harder each playtest. My intention is for it to be possible with WW-I tech.