...then it also deserved a two-part animated adaptation.
You may disagree that AS\S/ is of the same quality of TDKR, but regardless, it deserved the same two-part treatment as TDKR.
I personally think it is Superman's TDKR, i.e., a definitive story for Superman that encapsulates who the character is and what he's about and does so in an out-of-continuity, "imaginary story" fashion.
So why didn't AS\S/ get a two-parter? Is it because Batman is the surer thing, money-wise?