If you want to look good, diet's a must. PLenty of protein. Fish, chicken, eggs, milk, cheese.
I must say, though; I have a Kurdish friend in Turkey who served in the Army, and he's really, really lean. He is also the strongest guy I ever met. He used to always give much bigger, bulked up guys arm wrestles and beat them every time.
I'd much rather feel as if I could take on the world than look. Though I understand that some people feel good by looking good.