This deserves a thread, there are a lot of time-killer mobile games out there... I'll start with my list.
1. Inotia 3 and 4 (pretty good, good history, good combat, action-based)
2. Simcity (a good time killer when you're bored, its well made)
3. Terraria (oh god, this is so naughtyword good, I wish they had more updates for the phone)
4. The Bard's Tale (the sarcasm, the laugh, the history and the protagonist are so naughtyword well)
5. Kairosoft's game (those are good games, well for time-killing)
6. Head Soccer (this is so vicious)
I could list Zenonia but the freemium feature fucked up my playing time.