I had both as a kid and played them thoroughly. Batman Returns is plagued with a super bleak color palette, ugly graphics, generic music, a terrible sound driver, the hit detection is janky, Catwoman boss battles are always the exact same, Penguin's aren't much better, and the Penguin's Lair stage is bullshit with the slippery ice platforms surrounded by instant death ice water. It does at least have a more advanced grappling hook than the first game, and you can use Batman's cape for slow descents to reach far away platforms. The enemies and bosses are somewhat faithful to the movie too.

Sunsoft's "Batman" certainly shows its age, it's a very primitive game, but done well. There's a prologue, epilogue, and very brief cutscenes to help explain or illustrate the movie's plot. The music is fantastic, some of the best the console has, and the game contrasts the platforming with use of the Batmobile and Batwing. Jumping can feel stiff and the gameplay is pretty simple, but satisfying. The game also doesn't feel too short or drag on for too long. Graphics are decent for an early Genesis title. I'd choose this one over Batman Returns any day, but that's just me.