I started playing WoW and I like it. I also play Pro Evolution Soccer 6 now and Trackmania Nations. They both are fun and challenging.
My likes are normally tend towards games with a good storyline. The Thief series and Mafia are my all time favorites, although I quite enjoy the FIFA series (EA) as well.
My favorite is Counter-strike 1.6, me and my friends used to play it on LAN in college hostels. Gone are those days .