Take it from someone who's braved the learning curve: This game is amazing, to the degree that it just might ruin all other grand strategy games for you. It has an incredible amount of depth to it, spanning 400 years of history and involving, trade, warfare, diplomacy, and colonization to create a seamlessly integrated whole. Every game is different, and with hundreds of countries to choose from, the number of fresh experiences and challenges is virtually limitless. I can't recommend it enough. And with free patches adding to the game regularly, it's always set to get even better.
And I should add - while the DLC all add great content to the game, they aren't required to enjoy it. The base-game is a masterpiece in itself. In fact, it's better to get to know the game in its vanilla state, then activate the DLC, as you won't be able to fully appreciate what they add until you've got a handle on the game's core concepts.
This game is fantastic.