Started playing it in 1999, still playing it today. I can honestly say this is the one game that never gets old.
There are so many strategies, you can never really master the game. Once you think you've come up with an undefeatable strategy someone else will find a way to beat you... which results in you having to re-think your entire strategy to come up with a better one. Everyone I play with has their own style of playing and their own favorite units/civilizations, but at the same time there's no way to predict what a player will do because people often try to come across as strong in one sense while secretively preparing a different type of strategy altogether. (If you play AOE2 multiplayer you probably know what I'm talking about)
All around, 10/10.