I like a decent progression system myself, and while I loved AoE3 more than 2 (but not more than Mythology) I won't pretend like it was balanced. I don't think there's been any RTS that has really even attempted something like it since, which is a shame - I'd kill for something like Battle for Middle Earth II's create-a-hero with the amazing persistent statistic records in modern RTS games. Then again, the "modern RTS" is itself a dying breed.