I'm just going to throw this out there, maybe The Death of Superman isn't that great a story and aside from the impact of the initial comic, has never produced a valuable piece of art? I have read the graphic novel, and it's alright? It's dated, very '90s, and has a lot of characters in it that the casual fan won't know, but is reasonably compelling anyway, with a few brilliant moments. Part of the problem is that Doomsday is just kind of a nothing villain, he's big and strong, but that's about it; he doesn't speak, has no real history and is only a threat due to his power, it's just kind of dull. So, can Bruce Timm and company do better with the story? A little? The Superman the Animated Series team naturally produce a quality product, but the story is still reasonably uninteresting to begin with, so never really gains new heights. Bigger budget means that the characters have some slicker design, but a change of voice actors drifts the film a little far away from the series.
As Superman is dead for a reasonable portion of the film, much of the action follows Lois Lane and her search for answers. This is also where the small cast hurts the narrative, as Lois only really has Jimmy Olsen to talk to and the pair track down Luthor and resolve the mystery in all of ten minutes of screen time. That's the problem I have with most of the adaptations of The Death of Superman, they cut out the extended DC universe and the broader stories that can be told with it. One of my favourite parts of the comic is when Blue Beetle (Ted Kord) steps in to hold up Doomsday for as long as he can so that people can escape, despite the fact he has no powers and Doomsday has already torn through several heroes. In an expanded setting without characters like Ted Kord and Guy Gardner, there is no one other than Superman and Lois who can drive the story. In the animated features, I'm baffled that at least Flash, or maybe Batman couldn't show up to help out for a little bit.
Superman Doomsday is an ok film, which suffers more from the material from which it is adapted than any mistakes or missteps with the production itself. I don't honestly think that Doomsday can be made interesting, or that keeping Superman dead for less than a year between films will carry any narrative weight. I'm yet to see The Death of Superman (2018), but Superman Doomsday is definitely a better watch than Batman V Superman, if you absolutely have to watch any of them, I naturally lean towards the Bruce Timm version. Personally, I'd prefer it if DC and WB stopped trying to make this story in film form, just let it rest for a while, at least until there is a Superman that resonates with the public strongly enough that people will actually care when he dies. Also, don't spoil Doomsday or that the film is about Superman's death in the trailer, seriously, that was dumb.