How much should your weight match what you look like?

How much should your weight match what you look like?
for example, for an average-build guy who is pretty tall, would it be better to weigh 170 and look like 190, or weigh 190 and look like 170?

It really depends. Different people carry their weight differently. Weight, the number aspect of it anyway, can be very deceiving. I'm 6'0" and I weigh 170, but I look heavier because I have an athletic build. I'd say looking healthy and being healthy are your main concerns, so for a tall person maybe be 190 and look 170.