So I just finished watching Golden Boy (1995), since I was curious about it and was very often recommended on various lists of retro anime to watch. It turns out that the show is obnoxiously horny, reaching "I can't believe it's not Hentai" levels in Episode 5 and that the show revolves around this seemingly incompetent dude that basically thinks with his genitals and always ends up getting the girl. The comedy is also basically 90% sexual and with such a setup, you can't really expect much else than objectification of women.
The animation quality is neat and the ED song is catchy though. 5,5/10
The above description might sound familiar if you've watched Great Teacher Onizuka (1999), which is similar in concept, except it includes a pretty good story and interesting characters. Unfortunately, it also is obnoxiously horny (which makes it creepier than Golden Boy due to the setting of GTO), is very ableist towards one of the students of Onizuka's to the point where episodes centered around them become unwatchable if you have a single ounce of liberatory ideology in your head and the show has some really bad filler episodes.
7/10? Sure. 8,69/10, like the MAL rating says? No chance in hell.
I don't really have examples of underrated shows or manga that are noteworthy enough to warrant me complaining about unfortunately.
I only watch shows that are recommended by friends or have high review scores, so nothing underrated, except that Evangelion and Madoka should be 11/10.
Overrated:
Hunter x Hunter is just ok for the most part, and the Chimera Ant arc is the low-point of the series.
Attack on Titan is boring and the story doesn't seem to have been planned ahead of time, with new plot elements just being thrown in because "wow wouldn't that be cool".
FMA Brotherhood is just ok, and is severely undercut by the ultimate villain's motivation being non-sensical anime bullshit.
Cowboy Bebop is a technical masterpiece but I find it so boring I couldn't finish it on a rewatch.