OK well, what I'd like to know is a gameplay-related reason not to like Sonic 1, I don't see how a three frame animation after the credits could swing someones overall opinion either way. The reward in both these games lies mainly in the enjoyment of beating the levels and collecting stuff, not so much the story/cutscenes.
I was replying to your argument about SMW being easier to beat and still get a good ending (didn't know there were different ones), which I don't see how it makes the game more rewarding when there's less effort involved.