Doom Patrol is the best of the DCU originals in my opinion, by far. BUT the other shows (Swamp Thing and Titans) are also great to watch.
As far as the other live action shows on here not DCU originals. Krypton is probably the best pick. Beyond that would recommend, Wonder Woman, Lois and Clark and Constantine. The others are all good IMHO, but those are the three that held up the best.
For the animated series, full disclosure I am not as much of an animated guy. But of the ones I have seen Batman The Animated Series you can’t go wrong with, Superman the Animated series is also excellent. And the Fleischer Superman shorts are also a fun watch even after all these years. Batman Beyond… also a good watch.
As far as the movies currently on here (given they rotate read this list later and something new might be on and something currently on gone). But my picks from the ones I have seen… Superman I and II , Justice League vs The Fatal Five, Batman: Gotham by Gaslight, Green Lantern: First Flight, Justice League: The Flashpoint Paradox, Batman: Mask of the Phantasm, Watchmen: Tales of the Black Freighter.
As far as elsewhere… sure you know this one but if you got Netflix the Arrowverse shows are all good, special recommendations to Legends of Tomorrow and The Flash. Also on Netflix… iZombie is good.
And on TubiTV for free you can see Powerless… which is a hilarious show that I highly recommend.
Also if you want some 80’s cheese the original Swamp Thing film is on YouTube 100% legal and free to watch.