has parked the car there for two hours

B is better. A is mildly confusing, since he isn't parked... the car is... But he's been at it for two hours.... so there's almost an image of him **parking** the car... moving it in and out of the spot ... for two hours. But even that's not what you said. it's just not clear.

A) this construction only makes sense if you are centering a complete thought around the agency and actions of the subject "he," as in "He parked the car there two hours ago and went inside to eat" B) makes more sense generally speaking, especially if the actions of the "he" in the first example is not really the subject of the complete thought, but the car is the main focus, as in "The car has been parked there for two hours, but the sign says 'one hour parking' only"

"To park" is a short event, referring to just those few seconds it took for him to pull the car into the parking space, so you would not say this with "for two hours." As u/amb3rlamp5 says, if you change the time reference to past tense, this would work: "He parked the car there two hours ago." Normally, though, you would say the B option, since this literally means that the car has been sitting in the parking space for two hours.