All this will be completely subjective but IMO the first, original DK Arcade game remains the finest DK game ever made. Without it's success, subsequent DK games would not exist.
Obviously without the first there cannot be more, but speaking of objective overall quality you cannot deny Country Returns as a wonderful product.
Also, I welcome Nintendo experimenting and creating new characters and art styles for their games as they did in Country Returns. New and original ideas over rehash, I say. I'll take brand new enemies and new art over reused music and art as seen in just about every NSMB game.