Here is what should of happened in my eyes, he drops her off then goes to make sure the planet is taken care of. Here Robotnik is taken care of by his death from the explosion and then he comes back to her and wants to take her home. On the way he has these feelings looking at her smiling and when they arrive at her house she's just about to go in looking sad at the ground. He takes her cheek and lifts her and kisses her, then they go inside. All you can see is a shadow of them in a window just before, then the light turns off and beautiful music is playing and a sign says "Fin." above the house. This is where the game ends and Amy gets her happy ending.

I love this by the way it's very beautiful.