I dont care about playability so much, I spend my money on the game and I expect to get a few hundred hours of it before I put it down and don't pick it up again for a while.

I've been playing Doom 3 recently, and what I've noticed is that I enjoy being scared ooh:" class="inlineimg" />less. Who would have thought, but that is the aspect that just keeps me coming back for more, whether its creeping through hallways scared and freaked out, or charging through blasting my gun while screaming my head off... I love it.

To really think about it more I thought about games that I played for hours, and also games that I enjoy the most. There are several factors that these games had that I assumed were the reasons I loved them.

Detailed Plots
Character Modification/ Personalisation (Like the KOTOR series)
Extreme Difficulty (I like a challenge)
Decent Graphics
Great Audio Tracks / FX

If a game has all of or at least two of these than I am happy.