Its been a long time since I played this, but when I think of my favorite RTS' of all time, this game always comes to mind. Resource acquisition was unique and different. Units power level varies widely, making battles dynamic, wild, and unexpected. Though all the factions consisted of having a few mechanics thrown together from other factions, they all played a bit differently, and there was a ton of them. And the persistent heroes was genius. Heroes in Warcraft 3 were nice, but in Warlords, they stuck around after battles, and had good amount of customization.