Considering the Game of Thrones series finale aired May 19 (unfortunately for HBO), however, I would say Lucifer should be pretty happy about keeping an edge over arguably the biggest show in TV history.
It was going strong in the reports from May, and the numbers reported from June so far are definitely solid.
The closest Lucifer came to losing the top spot was the week of May 20 – May 26, when it was not even 2% above Game of Thrones.