My new favorites are Kingdoms at War, which can also be played online, Pocket Legends, which is on both the iPod/iPhone and Android. Also Future Combat, made by the same people as Kingdoms at War.
Kingdoms at War is a game where you create a kingdom to battle with other users. You join a clan and do wars and Plunder Wars, which is designed to help you grow very fast.
Pocket Legends is another MMO, which is fully 3D. You choose between a bird archer, an Enchantress, and a warrior. The best class in my opinion is the Enchantress, which is the mage class. What you do is lvl up, put stats points into your classes stat. If you really wanna be a good class, be a mage, and lvl up archer stats. Then you use Bows and magic. It owns.
Finally Future Combat is exactly the same as KaW. Biggest difference is the Currency Worth. 100,000 in FC is like 1 million in KaW. I hope you try these games out. They are all very fun.