I was lukewarm about Man of Steel when I first saw it. There were things to like about it and things to dislike about it. The special effects were top notch. They definitely put good money into them.
My Superman foundation would be a mix of Lois and Clark: The Adventures of Superman and Superman: The Animated Series. I actually re-watched nearly all the episodes of Lois and Clark like 2 years ago. I hadn't seen any in over a decade but a cable channel started playing them. It holds up ok actually. S:TAS still has some of the clearest, simplest and yet strongest characterizations of the Superman mythos and holds up real well also.
I never cared too much for the Christopher Reeve Superman movies aside from the John Williams score. By the time, I saw those movies, they were too corny and preposterous. Although Christopher Reeve really did make for a great Superman. A friend of mine who is a really big Superman fan lent me a copy of Superman 2: The Donner cut to watch saying it was better. I was curious about it so I checked it. This was sometime after Man of Steel came out. I hadn't seen the original Superman 2 in some years. I remembered some things about it but couldn't really say what was new or different about the Donner cut from when I first saw the other version. For the time when it came out and compared to the ending of the original Superman with time rotation based on the spinning of the Earth, I get why it is regarded as the better Superman movie. It definitely plays more to kids though which is another reason why I don't think it holds up well compared to modern animation movies which plays to both kids and adults much better.
Another factor working against Superman 2 is the fact that there has now been more stories about Zod or Krpytonians. Lois and Clark had a 4 part arc dealing with encountering some Kryptonians (though there was no Zod in this group). Superman: The Animated Series had generals Jax-Ur and Mala to fill the roles of Zod and Ursa. Later Smallville had Brainiac attempt to free Zod and a storyline around that in Season 5 to the start of 6. Even later on the show, all of Season 9 dealt with a clone of Zod and other Kryptonians and Clark's struggles with them and their allegiance to Zod. All in all, Season 9 ended up being probably one of the top 3 seasons of Smallville too. That was one of the better storylines on the show. In comics, Zod's popped up a few times. Richard Donner did a 5 part story with Zod. Later, there was the New Krypton storyline that went on for sometime in the Superman series of comics.
What this means is that there have now been a lot of different stories and interpretations done about Superman encountering Kryptonians or Zod. Each time, there's tweaks and twists from what came before to do and try something new with the material. Thus, looking back on Superman 2, there are still some things that are ok about it but I just think there's a lot better material out there now which lessens its appeal and impact. In some respects, that's also a problem with Man of Steel. There are good ideas and a better standard or characterization of Zod or encountering other Kryptonians that exist and are accessible for fans to compare to the movie. Unfortunately, it tried to do some different stuff along with some expected stuff (the "fanservice") but ultimately it just doesn't compare as well with what has come before.
In the end, I just wanted to note that I actually ended up re-watching Man of Steel for the first time since I saw it in Theatres about 2 months ago. Watching it, I did appreciate more some of the criticisms that people made of Snyder's direction like the shake the camera and then zoom in on something shots. I can't say I noticed it that much in the theatre the first time but watching it again at home, I definitely did. Yet, I also found myself more forgiving of the movie. And by the end, I thought I might have judged it too harshly. Maybe I've just made peace with its flaws or just accepted it for what it is but there's still some fun to be had and the movie is still quite entertaining. We're not talking Batman Forever or Batman and Robin levels of bad. Superman Returns made the mistake of trying to keep the series in the Christopher Reeve direction which makes it very hard for me to re-watch. I've tried sometimes but I just give up after awhile. Yeah, maybe it isn't at The Dark Knight or Guardians of the Galaxy level but somewhere in between all that. It's not a movie I'm going to want to see a lot of but at least it's one I'd be willing to rewatch and probably still enjoy again another time which, to me, is a success because a lot of movies I've seen don't even get to that point.