185110c3__of_the_Year___Dusty_Cartridge__Borderlands_2
[Mechanic] Quests: [Borderlands 1] Basic objectives and missions. [Borderlands 2] 
More dynamic missions, ones that affect the overall storyline depending on the outcome (think Fable). Time limits introduced for certain objectives.
Why Borderlands 2 will be Game of the Year - Dusty Cartridge
Borderlands 2