The original Kirby for the Game Boy was an incredibly accessible, incredibly short adventure with Kirby in Dream Land. The graphics were beyond anything I had really saw on the system, they were so distinguishable and clear, so cute and colorful despite the grey screen. I described it in a previous review as a game that, if in color, would be SO colorful. Kirby's Adventure for the Nintendo Entertainment System is the game I feel HAL was probably trying to give to Kirby, a more fleshed-out adventure with a plentiful amount of incredibly sugary worlds.
I think how much you will enjoy this game depends on how critical you are in general. There are problems: The game can have slowdown when too many enemies are on the screen and for the most part the game is pretty easy, but on the other hand the game is so colorful, graphically is probably the most impressive NES game ever made, the soundtrack is fantastic and the controls are perfect. The addition of Kirby's inhaling ability gives the game some variance the original did not have. This game could easily be a top 10 NES game and I would advise it to everyone.