1) The faster you finish the game the better the reward.
2) The Worst Ending doesn't showcase Simon, just the tomb of Dracula.
3) In the Bad Ending we can clearly see Simon so that's just a bonus, indicating we've done a good job or you can say a reward.
4) And the final one, which all of us Castlevania fans have missunderstood all this time, is very nice because it teases us that even tho we beat the game there are more games to come and more adventures to take, it just shows that Dracula will be ressurected again, which means another game, like haven't you all seen those movies which hint at another sequel? It is that simple.
5) With that said, the colors of the background make sense too, the best one being more colorful than the worst one being dreadful and the endings narrative is just bad translation.
6) Also everybody knows that the whole game is a mess of poor translations, which made the game bad, but that's not true, we just experienced a very bad version of it, and I have proof.
7) There is this website that shows all of the mistakes in the US version and if you play the japanese version of the game you would see that is not such a bad game, even tho the game design is kinda broken is some parts, but the idea at least it's very revolutionary for it's time just like Metroid and Zelda, even tho the exectution was not very good. bisqwit.iki.fi/cv2fin/diff
I wanted to speak about this, because I just finished the game 2 days ago and did research on it and I found it very bizarre that everybody says that the endings are screwed even tho they are perfect.