Not sure I'd call it my favorite space opera - but Doc Smith's Lensman series seems like the prototypical space opera. Multi-generational, clear-cut heroes and villians, action taking place across a multitude of worlds, with a multitude of alien races, and of course, absolutely purple prose.

Y'all asked about the use of Arabic words in Dune - the Fremen religion is given in the book as Zensunni (obvious portmanteau of Zen buddhism and Sunni Muslim). From the Glossary at the back of my copy: ZENSUNNI: followers of a schismatic sect that broke away from the teachings of Maometh (the so-called "Third Muhammed") about 1381 B.G The Zensunni religion is noted chiefly for its emphasis on the mystical and a reversion to :the ways of the fathers." Pretty sure Herbert was being very deliberate in that choice, and using (in part) the story of Dune to explore the rise and spread of desert religions (q.v. Islam, Judaism and Christianity here on earth). I don't know that it's a thesis that is seriously considered in ethnographic studies today, but I can recall at least one other author (R.A. Lafferty) using that theme in a short story (Rivers of Damascus).