I got addicted to World of Tanks recently. Definitely the best online game I have played for a while, besides WoW and MapleStory (I'm still a kid at heart).
Everyone should play WoT. It's AMAZING.
But it's freemium free-to-play. It took me several hours to finally get a Tier 5 tank. Be prepared to spend lots of time on it if you play.
If you have CnC Generals ZH, be sure to download the Rise of the Reds mod. The best.