While Superman may not be my favorite Superhero, I do enjoy both his live-action and animated movies, comics, and animated shows (I didn't like Smallville or Lois and Clark) but I have to say, when I learned that General Zod was the villain in the new Superman Movie, I was pretty disappointed.
There is absolutely nothing wrong with General Zod as a villain or character. It has been years since I've seen Superman II, but from what I remember, there wasn't anything bad worth mentioning about him. But in the past five superman movies, we have only seen two of his enemies from the comics, Lex Luthor and General Zod. In three of them, Luthor was an enemy, and now Zod will have been the enemy twice. They are both good characters, and it is understandable why Luthor was used so many times, he is the arch-enemy of Superman, and most popular villain of his, but people get tired of seeing the same things so many times, and yes, Luthor is not the enemy in this movie, but Zod is, and we have already seen Zod.
Superman does not have a rogues gallery even close to the caliber of Batman or Spider-man, but he has his share of good villains. Characters like Mongul, Brainiac, Bizarro, Metallo, Doomsday, Darkseid and even Lobo would have excited me more than Zod because they would be something new and fresh. This is where Batman Begins and the upcoming Amazing Spider-Man helped draw more interest, they had a new villain. The last time I brought this up someone argued that nobody complained when Joker and Two-Face were the enemies in The Dark Knight, and my argument for that is nobody complained because it had been awhile since we saw them, and yes, it has been much longer since we saw Zod speaking in the amount of years, but in-between Zod we got a super computer that wasn't Brainiac for some odd reason, Luthor again with Nuclear Man, and Luthor one more time. Between Batman and The Dark Knight we saw The Penguin, Catwoman, Riddler, Scarecrow, and Ras Al Ghul (I'm not even counting those awful portrayals in Batman and Robin, or Two-Face since he appeared in the Dark Knight too). So we may have seen the same villains in The Dark Knight, but we had seen many of Batmans other villains in his previous movies, so we didn't mind. But we have not seen anyone but Luthor and Zod in the Superman movies, and it is a shame because Zod is not a bad villain, but a new face would have been so much better.
And even if they were saving Darkseid for the Justice League movie, it would have been better to have him in this movie so that in the Justice League they would not have to tell his background story and just cut straight into the Justice League story.
It's working well for Loki in the Avengers anyway...