By the definitions I set here, Jaws is the only other summer blockbuster in contention for "best". If judging purely on filmmaking quality then I'd say Jaws has better performances (especially Quint's monologue) but Star Wars still has solid performances (which improved with The Empire Strikes Back) and in terms of seismic influence, Star Wars beats it. But Jaws definitely laid the groundwork in a John the Baptist sort of way. :)