Yes it was,, star wars was a massive hit going all the way back to opening weekend for episode 4.

Star wars was immediately a cultural phenomenon from its inception.

Here is a quote from it's wikipedia page:

Star Wars remains one of the most financially successful films of all time. The film opened on a Wednesday in 32 theaters expanding to 43 screens on the Friday and earning $2,556,418 in its first six days to the end of the Memorial Day weekend[223] ($12.3 million in 2022 dollars). Per Variety's weekly box office charts, the film was number one at the US box office for its first three weeks. It was replaced by The Deep but gradually added screens and returned to number one in its seventh week, building up to $7 million weekends as it entered wide release ($33.8 million in 2022 dollars)[3] and remained number one for the next 15 weeks. It replaced Jaws as the highest-earning film in North America just six months into release,[224] eventually earning over $220 million during its initial theatrical run ($1.06 billion in 2022 dollars).[225] Star Wars entered international release towards the end of the year, and in 1978 added the worldwide record to its domestic one,[226] earning $410 million in total.[227] Its biggest international market was Japan, where it grossed $58.4 million.[228]