I used to own about 900 DVDs but already gave away about 200 of them to relatives and friends. I will get rid of a few hundreds more in the future, mostly films I don't care about anymore or are on TV all the time anyway. In the end I'll only keep the most beloved classics which are probably around 250 DVDs: US classics from the 1920s to 50s (e.g. from directors like Ford/Huston/Hitchcock/Capra/Cukor/Wilder/Curtiz/Wise, Laurel & Hardy/Chaplin/Marx Brothers/Danny Kaye movies, Astaire/Kelly/Donen/Minelli musicals, my Tom & Jerry and Disney Cartoons DVD Collections etc.) and US/French/Italian/Japanese classics from the 60s/70s from directors like Peckinpah/Scorsese/Allen/Kurosawa/Truffaut/Leone and so on.
Generally I plan to keep only DVDs with movies you don't see on TV anymore these days and are not available via streaming services. The libraries of most streaming devices are a joke to fans of classic movies imo.
On Blu-Ray I only bought about 30 movies so far. Most of them are animation movies, incl. some of my most favorite Disney movies like Pinocchio and The Jungle Book plus the afaik even in Japan still incomplete, but beautifully designed Ghibli Collection (not my picture - I buy the German edition of these Blu-Rays which looks very similar to the Japanese original). Animation movies look gorgeous on Blu-Ray.
