For me it's probably a tie between hearing and eyesight. I have excellent hearing and can hear higher and lower than most people, apparently and my eyesight is 20/10 which means I can see more detail further away than people with 20/20 vision.
I wear glasses, but even with glasses I think my best sense is vision. I pay so much attention to images. Even as much as I pay attention to sound, I don't think my sense of hearing is as acute as my eyesight.
Probably a tie between hearing and sight, although my sense of touch is very acute as well. My sense of smell is very dull compared to everyone else in my family; they will notice scents and odors that I would never detect in a million years.