What was/would be the best, most valuable compliment you coud get?

For me, the best would be what Jack Nicholson said to Helen Hunt in "As Good As It Gets": "You make me want to be a better man."

Dad, thanks for giving me the confidence and skill to ... be the handiest girl I know.

Professionally, when I came in late to work, having run some simulations on the home-made Imsai. Slightly perturbed boss looked at my printouts and said "You did a week's worth of work in one morning".

or time he said:

"You do great work, not very often, but it's fantastic when you do." :-)