I like the prejudice in here. No one except Grimlock has even heard the sound effects yet and there are already calls for not putting them in the game, and that they are just going to come off like automated famiclone tweaks.
I'm going to tell you all the same thing I've told people who have emailed/PM'd me for being "disappointed" with the music changes: This isn't Metroid 1
This is Rogue Dawn. The objective here is to leave behind the notion that people are playing the original Metroid game, and enjoy a completely new experience with higher quality graphics, sound, and gameplay.
Castlevania 3 did have many of the same sound effects as the original game, though many of them were modified for the better. I would say in that case they wanted the player to be reminded of the original game, as the gameplay and layout is similar, as were the game's graphical styles. But look at Castlevania 2, a much different direction, and much different sound effects for the most part to fit those changes; the enhancements on the sound and music ended up being the best thing about that game. Would you rather play Castlevania 2 with Castlevania 1 sound effects?
Long story short, I'm aiming for a departure of the original for a newer experience, and not a straight reminder, and I believe that's what Grimlock and Snarfblam are also trying to accomplish.