I think AOE2 is relatively well balanced.
Some civilisations are weaker than others, but in general you can't win just by choosing a better civ.
I personally love the Goths. They get cheaper elite infantry (the swordmen) and a lot of bonuses on unit construction speeds, + a slightly higher population limit.
Build 3-4barracks near the enemy base and you can pump out infantry like no other civ.
It's pretty weak otherwise though.
Depends on the map type and how you play.
The Teutons tend (for me) to be the best all round civ as those knights are awfully powerful and they have nice civ bonus.