These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anti-Climax Boss: After you've completed all of the levels, you have to fight Bowser. Since this game has no life meter and no power-ups, Luigi cannot lose, no matter how many times he gets hit. Oh, and this only applies to the NES version — in the other versions of the game, the entire confrontation plays out in a cutscene.
They Wasted a Perfectly Good Plot: How the hell did they mess up Luigi's first starring role, and Mario getting a time machine? And going through geographically/historical significant places on Earth to boot... oh right, educational games. On the bright side, the cut scenes and voicing are So Bad, It's Good.