Surprised there's not been a mention of a couple of RPGs I've encountered - Zenonia 3 and Destinia, both from Gamevil and both free. Pretty simple games with a lot of similarities - both have a basic crafting and pet system, quickslots, attribute & skill point allocation and D-pad movement with 1-button basic attack combos. They've got a very Korean feel to them, so expect a lot of "Fetch/Kill
X of
Y in
Z area" format quests all bunched together in convenient hubs and a whole bunch of grinding on top, but they're nice little time sinks.
Keep in mind that they both feature an in-game shop, selling bonuses for real cash. Some of the bosses are a right pain to do without the all-important resurrection scrolls, which are only available for cash currency, but they're all possible with just the free stuff you can pick up on the way.
The other time-sink I've encountered recently is Zombie Farm - grow crops to earn cash, build a little farming field and, of course, plant and harvest a zombie army to raid your neighbour's farm and get brains. Pretty solid gaming from Mobage - connection required for every launch, another in-game shop with cash-for-win boosts but well worth it. It's much more of a long-term game though - plant your crops and forget about them for a few hours while you do other things, then harvest them later. You even get a ding in your notification area when your zombies are very hungry for brains
