I can think of a few, though evolving taste can also make we view a work more positively than before:
-Captain Planet and the Planeeteers (old): "Yay, I love this show! Earth, fire, wind, water, heart! Let your powers combine!"
Captain Planet and the Planeteers (now): "Well, this is showing its age, considering that in-universe it takes place in sync with the production year (e.g. the Rio Conference). I mean, well, the villains are lacking any kind of subtlety, and some of them use pollution as the end rather than the means, but, yeah. I don't think this show is nearly as bad as many people claim, but my childhood experience is still different."
-The Chronicles of Narnia (old): "Yay, talking lions! White witches! Green witches! Badgers! Dwarfs! Fantasy adventure!"
-The Chronicles of Narnia (new): "Well, this is quite an interesting take on Christian theology, wrapped up in a children's story. Writing's a bit basic for me as an adult now, but nice job Mr Lewis. Well, nice job except The Last Battle, but hey, we all need our least favorite book in a septology.
-Dragonball Z (old): "Awesome! Guys are fighting! Stuff's exploding! Yelling, screaming, bloody violence, yay!"
-Dragonball Z (now): "Jesus Chris this is stupid. Half the time is spent talking, and it's not even good dialogue. It doesn't help that you're either a saiyan or you're useless, and the means of defeating the enemy is to just keep getting stronger rather than having a set power level and relying on means other than brute force."
-Spider-Man: The Animated Series (old): "Yay, Spidey! Action! Action! More action!"
-Spider-Man: The Animated Series (now): "Ugh, this has aged terribly. Monologues are dull, fighting is lacklustre, stories are formulaic, I've got no reason to watch this since Spectacular Spider-Man is a thing. Also, it's batshit insane. I mean, Mordo, Doctor Strange...what?!"
-Mortal Kombat (old): "Blood and guts, gore, I'm gonna dress up as Sub-Zero cause he's AWESOME!"
-Mortal Kombat (now): "Well, this is absolutely rediculous. I think there's a good idea/story nestled in her somewhere, what with the realms and whatnot, but it's primarily a fighting game, and aside from Soul Calibur, fighting games aren't really my thing anymore."
-Pokemon anime (old): "Gotta catch 'em all!"
-Pokemon anime (now): "Holy Moltres, this is cheesy! Cheese I could tolerate if not for the knowledge that the reset button is being hit between each region now."
-Power Rangers (old): "Go go power rangers! I'm gonna pretend to be the blue ranger while we fight Rita in the playground!"
-Power Rangers (now): "Well, this is stupid. Over the top and cheesy fun, but still stupid. And while we've had a few, decently written series, it's staggering to see how little the series has evolved in quality of writing (looking at you, Megaforce), when believe it or not, cartoons and "kid's shows" CAN be intelligent."
-Resident Evil movies (old): "Kickass!"
-Resident Evil movies (now): "Well, this is stupid. Doesn't help that the movies have gotten worse with each installment, and even if this wasn't a supposed adaptation, Alice is a Mary Sue in every sense of the word."
-Sonic the Hedgehog (old): "First game I ever played! This series will always be great! Sonic 4ever!"
-Sonic the Hedgehog (now): "Well, the Boom cartoon still gives me a chuckle. But this series has had such an identity crisis and so many incarnations, that while I still like Sonic overall, there's just far better series out there for me to invest my time and money in."
-Starship Troopers movie (old): "Human vs. bug action! Yay!"
-Starship Troopers movie (now): "Well, that was a very...'creative', adaptation of the book. But it's a good action flick with some nice sattire. Certainly the book's equal IMO, if for very different reasons."
-Star Wars prequels (old): "These are even better than the OT! They've got lasers! And droids! And hoo...what, what's a hooker?"
-Star Wars prequels (now): "Well, episodes I and II aren't nearly as good as I remember them, though Ep. III still holds up. Not nearly as good as I remember them, but still the recipients of way too much hate."
-Star Wars original trilogy (old): Lasers! Laser-swords! The Force! Action! Return of the Jedi is my favorite!"
-Star Wars original trilogy (new): "Huh. That holds up surprisingly well. It's effectively a modern day myth with reliance on tropes, but still an excellent piece of space fantasy. A New Hope is my favorite now though."
-Warhammer 40,000 (old): "Space Mareens! For the Emprah! Kill the alien!"
-Warhammer 40,000 (now): "Well, that took creative license from Dune and Isaac Asimov. Very well fleshed out universe, but for God's sake, enough of the Space Marines! They're a power fantasy. I admit to being swept up in them, but come on guys on the Internet, dialogue still needs to be...well, dialogue."
-Doctor Who (old): "This is wonderful! This is amazing! Doctor devah!"
-Doctor Who (now): "Well, this is silly. But still a good kind of silly. Not the best show ever concieved, very hit or miss at times, but as an adult, I can still appreciate it."
-Rowan of Rin (old): "Fantasy adventure, yay!"
-Rowan of Rin (now): "Well, this is still a kid's book series. But certainly a thematically rich, intelligently written one. Always felt it was better than Deltora Quest, but as an adult, I can articulate why now."