Far Cry 2
Far Cry 2 is great when it shoots from the hip, but the majority of the game is structured around a rinse-and-repeat mission structure that is predictable and, at times, laborious. To be clear, it's not the mechanics that get old (with the possible exception of driving). It's the continual sensation that you're defeating your own purpose by working in equal measure for two rival factions vying to destroy one another.
Your overarching goal is ostensibly to find and kill The Jackal, the man responsible for arming the conflict, but you spend the majority of the game completing missions are only tangentially associated with that goal at best. More frustrating than the weak narrative context, though, is the repetitive structure of the missions. Tasks and objectives are not only recycled, they are arranged in the same... exact... order... mission after mission: acquire contract, drive, meet buddy, drive, destroy secondary objective, drive, destroy primary objective, drive, save buddy, drive, acquire contract.
Halfway through the game, and again at the end, the game temporarily abandons the above structure and becomes refreshingly unpredictable and extremely enjoyable. The story advances rapidly and mission structures detour into unfamiliar territory. Would that the entire game had been crafted with equal love rather than bound to uninspired mission templates.