Both panda and jura are correct. It can also mean that someone was a success in some social situation. It does not have to mean popular to the general public, though that is often how it is used. A good example of this last meaning would be: "I brought my boyfriend over to meet my parents. He was a hit with them."

Panda is right. Don't confuse this term with 'a one hit wonder' which means that the person has only achieved one brilliant thing.

"someone is a Shit"

Means that person is gotten very popular. That song is a hit, likewise, means that song is very popular, but whether or not it is the most popular track is unclear.