I love Rollercoaster Tycoon 3. I have all the add on packs, and can spend hours wasting time creating riding coasters, and building and exploring parks. The Wild add on pack is fantastic with the added option of letting you turn your theme park into a zoo. I have hours of fun waiting for lions to escape and eat my visitors, especially when they start moaning about the length of the queues.
At the moment I am working on getting my scores up on Wii Sports. I am a Pro in bowling, but my boxing skills are awful, with my son beating me all the time.