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.
Most Annoying Sound: The High-Power Grenade Lobber - EEEeeeEEEeeeEEEeeeEEEeeeEEEeeeEEEeeeEEEeee
Polished Port: Of course, the game was notorious for being Nintendo Hard. The home console version wasn't exactly easier, but with unlimited continues meaning you could play it without spending a fortune in quarters, it was certainly more enjoyable. One advantage it has over the arcade original is an actual soundtrack; in a developer interview, the sound engineer for the arcade game was instructed not to put too much effort into the music since the game's constant gunfire and explosions would drown it out anyway.
Those Two Bosses: Scarface and Cobra Head. Surprisingly, these two bosses are more difficult to survive than the Evil M.C.