As I speak:
Dreamcast: Shenmue 2 (finished it last night after 18 months on/off playing. Hurrah!)
Xbox: Halo
PS2: Grandia 2 (my flatmate's playing through it)
Genesis: Gynoug
Saturn: Christmas Nights (oops - mustn't have played anything since Xmas)
Jaguar: Tempest 2000 (it's been there for about the last 3 years)
SNES: Mario Kart
NGPC: MOTM
everything else is neatly stacked and cart-less.