This is a side-point but IMO if a game is genuinely great it should last someone 12–25 hours and remain exciting and awesome throughout. Ones that last less then that aren't a bad thing as clearly there's a demand for that short but sweet experience, but I don't like the fact that games lasting 5–8 hours are out there costing as much as the ones that last literally twice as long.
Nowadays I have to go looking up forum posts and shit to get an idea of how long a game actually is because it's not like they actually print 'oh yeah this lasts a few hours LOL' on the box.