Ikariam(.org) is an online multiplayer game. It's sorta like Civilizations, but everything takes alot longer. For example, building a town wall can take 3+ hours. This game takes quite alot of devotion, but once you get in to the game, it's fantastic.

Gameplay: 10/10

The game can seem a little dull, but once you get into a war or a battle, it's awesome.

Functionality: 10/10 This game/website get everything right.

I recommend you get into this game, however, be prepared to spend quite alot of time there.

Also, it's 100% free.