Boateng played for Las Palmas in the Spanish top-flight last campaign before returning to the German Bundesliga to join the Eagles as a free agent in the summer of 2017.
And the 31-year-old expressed satisfaction with a decent career which has seen him play across the four top European leagues including the English Premier League and Italian Serie A.
"In my opinion, without meaning to come across as arrogant, I could have played for Real Madrid, but I didn't do enough to achieve that," Boateng told Bild.
"However, I have reached a point where I am relaxed and satisfied with my career."
So far this season, the former Ghana international has scored six league goals in 27 appearances for Eintracht Frankfurt who are placed sixth in the league table.