Good space operas

Several people recommend their favorites at SF Signal.

Oddly, the story that came to my mind alongside Lensman series was a classic largely forgotten now (& one no one names in the link above): Eric Frank Russell's very funny "The Ultimate Invader". It's not a novel - just novella length. A smart aleck representing a technologically very advanced galactic empire vs a despot ruling a small group of worlds.

Also missing is the James Schmitz's very famous novel, "The Witches of Karres" (download). Light fun read.

Related: "best of" lists.