You can win a RTS by one single way - military. Whether domination, conquest or Kill the King.
Because of that, in any RTS there is only one goal: More units.
If you ask me, incredible boring. Played AoE for about 10h, and had enough. Spent some more time with 'Cossacks', since I liked the historical background more, but it got equally boring. No trades, no diplomacy, no space ship parts, no AI (like if only the military advisor of Civ3 would run the whole game).
That said, I'm biased. Since I got me first pc 12 years ago, I never really enjoyed any game that wasn't turn-based. Not only Civ, but Panzergeneral or Warlord in their incarnations. Out of the RTS field, AoE and Cossacks are surely among the better games. Jut can't stand any other genre that TBS.