http://www.wesnoth.org/
Battle for Wesnoth is a turn-based RPG that's like Fire Emblem. It has 15 campaigns, each taking hours to complete. The game is really long and can last for months.
You control an army and you must try to complete the tasks in each level. The tasks can be kill the commander, survive a certain amount of turns, get to a destination, etc. The cool thing about the game is that unlike Fire Emblem you can recruit as many units as you like, as long as you got the gold to pay them. Yes the units you recruit will take your gold away if you have more of them than the villages you have, so it's important you capture villages to get more money and recruit more units. Sometimes you get units with the loyal trait. These units fight for you without pay, so it's important to keep them alive.
The best thing about the game is that it's free of charge! You don't have to pay any money to download the game, however the Iphone version costs 5 dollars. Battle for Wesnoth can literally take months to beat, even if you play it nonstop.
The awesome thing about the developers is that they support 3rd party mods! They even have a page on their website that gives you instructions on how to make your own campaigns using the open source!
I played this game like 4 years ago when my internet was down for a few weeks. Pretty solid game.