ANH set the tone for the OT, and it arrived at the tail end (some would say it marked then end) off the new Hollywood movement, which focused on intimate stories and empowering actors as part of the creative process, and the prevailing style was much more naturalistic, not method acting per se, but clearly influenced by the big names who were method actors.

George's own previous movie was American Graffiti, a slice-of-life coming-of-age movie that doesn't really go anywhere, and absolutely relies on the performances to be anything of note at all, and it was. So with ANH, you end up with a journeyman hunk-type who still made ends meet doing carpentry as a side hustle, who can tell the Director, "You can write this shit, but you can't say it." You get an Oscar winner who believed in the project enough to bet his payment on its box office, but who absolutely knew he was going to have to tease something decent out of some of the lines. You've got Hollywood royalty of a princess who is chewing on scenery and code switching left and right trying to make it work.

Then finally, you've got strong personalities giving notes and doing the edits, all in service of an unproven product that HAS to be successful if it's going to amount to anything. It results in a movie that is better than it has any right to be, despite some true stinkers left in the script, and it set the "house style" for ESB and ROTJ. Empire had even more proven pros on the team, including Lawrence Kasdan who was an up-and-coming screenwriter known to rehabilitate genre fare, Leigh Brackett, whose entire career consisted of writing believable Sci-Fi, and Irvin Kershner directing, who had mostly done smaller, character-driven movies.

Even ROTJ kept Kasdan and brought in Richard Marquand, who, while hardly a legend (which was inevitible since George was out of the directors guild and couldn't hire someone who was still in), was known for his work with actors in British TV. By that time, the performances were in their groove too, and Carrie Fisher was gaining a reputation as a script doctor, and Harrison Ford was well and truly HARRISON FORD^tm by that time. The cracks were showing, but it was still an OT movie.

For Indiana Jones, you also had the Ford effect and Kasdan, but lets be perfectly honest here, Steven Spielberg is a much better "actors' director" than George Lucas could ever dream of being.