As a parent, I must STRONGLY disagree with the suggestions that you change the password! If my kids did that, computer access would be the least of their worries for a LONG time!
Don't beg for access back. That gets you nowhere, as we parents often find it more annoying than anything else. My advice is prove that you are able to handle the privilege of playing games. I.e., do your homework without needing to be asked, keep your room clean (if your parents expect it, I don't worry too much about my kid's room right now, but they are still young), generally just try to make your parent's lives easier, then after a couple weeks of that gently bring up the subject. If they say no, don't fight it, just keep up with the homework, etc, and eventually your parents will soften to the idea.
It sounds like the conflict was over time spent in the game and priorities. If you take care of your parents priorities first (school, chores, family, etc...) they will be more likely to provide time for your priorities (games!).
Good luck! Remember that the ideas of eGO (politeness, maturity, and respect) work WONDERS on parents! If you approach it that way, you'll be much more likely to get what you want!