The final volume of "Superman: the Animated Series" came out last week, and I've been making my way through the 18 episodes, many of which were new to me (I didn't really keep up with the series when it was originally running). The one thing that immediately struck me is that by the end of its run, "Superman" had really become Crossover Central. Six of the episodes in this set incorporate the Darkseid character, who isn't precisely a Superman villain; even if you don't consider that a crossover, the set has two more team-up episodes with Batman, a Green Lantern crossover, a visit from those Legion of Superheroes kids, and (snicker) Aquaman. (Yeah, they tried to make him tough and badass and all, but it's Aquaman. He has fish power.)
The downside of all these crossovers is that Lois Lane and Lex Luthor were almost completely wasted by this point in the series; Lois doesn't even appear in half the episodes. And more generally it was always a weakness of the "Superman" animated series that Lois didn't get enough to do; they had a pretty good approach to Lois's characterization and a great vocal performance for the character (by Dana Delany), but I don't think they ever had a good Lois-centric episode, something that would develop her character or her relationship with Superman and/or Clark. When they kiss in the last episode of the series, it almost comes out of nowhere.
On the plus side, this was one of the last TV cartoons to use a full orchestra for the score, and what a difference it makes. The "Justice League" series has most of the same composers, but due to budgetary limitations, they're working with electronically-generated music. No matter how good that is, it can't compare to the specific, memorable sounds produced by an orchestra; and the orchestral scores make these shows feel a lot less dated than many shows being produced today (because the sound of a computer-generated score is tied to the technology of the time, whereas a real trumpet sounds like a trumpet). Several of the weaker episodes in this set are bailed out by the classy music.