RuneScape. Simply because it's a great game, and if it was real life, it would have a better combat system. Then I'd stuff the rules and go around killing noobs. You can't stop me!
4. Scribblenauts
"Oh no! I hate that person! I'll just write DEATH"
I want that! NAO!
EDIT: Come to think of it, Blockland would be great :-)