My dad is a complete non-gamer. He once watched me playing Guitar Hero 3, and really wanted a turn. I laughed a lot, but he managed to finish a song on easy despite never playing before. He plays real guitar, which I really have a lot of respect for anyway.
He once tried my PS2 dancemat, too. I belly-laughed so much I choked on my tea.
My mum's fairly non-gamer, too, though she can kick some ass on games such as Tekken and Dead or Alive. My step-dad is a real gamer, though, owns a lot of consoles (apart from the PS3), and plays stuff such as CoD4, Gears of War, Dead Rising, etc.