The original tileset in Super Meat Boy isn’t too bad, and it fits JJ2 pretty well.
Unfortunately, it’s been scaled and palletised completely naively. It’s now blurry, distorted, and full of stray pixels. The layout is also poor in places, with closely related tiles place far away from each other.
My advice is to just try again and put more effort into making it look as good as the original. If a tileset is worth converting, it’s worth converting well.