I can't play Elite with mouse + keyboard. I tried with gamepad and it was almost playable. I think without a HOTAS stick it just isn't enjoyable. That seems odd, I played the BBC Micro version to Elite status on keyboard and most of the way there on Atari ST with its solid shaded ships, woot!
Still, for me:
Gran Tourismo 5 on the PS/3, I really gave it a go as I wanted something as much fun as the old Dreamcast MSR game. I nearly bought a steering wheel for it but decided that for me it just wasn't enjoyable and I shouldn't waste further time and money on it. Mario Kart has better handling dynamics and frankly is about as realistic.
Candy Crush saga held my attention for a few hours, but I can't see how people plough so much time and money into it.