As someone who doesn't like Returns, I think these are fair. I can't be objective of the movie for various reasons, but the more I think about it, I think it's correct to say Singer took on the aspect of the ending if II where Superman and Lois kind of move on with their lives (from my understanding, Donner would've wanted to continue the movie series without focusing on their romance like he did in the first two). It kind of makes Returns even more of a spiritual successor than I'd like to give it credit for.
Overall, I think the scope of the movie works as a type of Superman story I could be interested in reading for a comic mini, but its position as a movie to rebuild a new generation of Superman fans is really peculiar. It performed about as well as it reasonably could.