Like any good arcade game, Captain America and The Avengers was given a few ports to popular consoles, with varying amounts of artistic license taken.
SEGA GENESIS/MEGA DRIVE
The SEGA Genesis/Mega Drive version is, in aesthetics, the ugliest of the 16-bit ports. Animation is snipped, colours are drained, the music barely resembles the originals, and heck, they cut out the imagery of the movie scenes! While the game is essentially fully intact (as in, nothing that effects gameplay cut out), there are a number of minor differences, such as running attacks starting automatically, 10HP items available in the shooter segments, and Mandarin now becoming the easiest boss in the game. The most bizarre thing of all is that the beat-em-up parts of the game are all rather clunky, with the game pausing until your character gets up from being knocked down, very awkward physics and other such things, yet the shooter parts are actually better than how they are in the arcade.
SUPER NINTENDO ENTERTAINMENT SYSTEM
The SNES version is definitely excellent in how close it looks to the arcade version. Although shortened of animation, everything looks pretty good, the music remains the same, and the sounds, although far less than the amount of the Mega Drive version, are all high quality and you can actually hear what they're saying. The sad thing is, it just doesn't play good. They were kind enough to make a separate button for your projectile, but everything is just horrendously clunky.
Walking diagonally is a hazard, you can't run, enemies are given more invincibility time than you and love to abuse that fact when it comes to grabbing you or preventing you from getting up, every attack knocks you down, and to sum it up quite simply, you're screwed. About the closest it comes to being kind to you is the fact the 10HP items in the shooter segments from the Mega Drive version are brought over for this, but that doesn't change the fact that even in the easiest difficulty, it's harder than the arcade's highest setting. There is something wrong with that picture.
A beat-em-up? On the Game Gear? Having never played a Game Gear, I have no idea if this is out of the ordinary. But the discussion is redundant, as this, although it uses the same scaled-down music, same scaled-down sprites and even the same scaled-down and redesigned stages, is actually a platformer. The Avengers now defeat Red Skull and his cronies and the cronies of his cronies by walking along, jumping across conveniently large window sills and on buildings, fighting enemies a lot. But the thing is, the fighting is awful. The collision detection kicks in only when it wants to, and the only time it definitely works is for projectiles and flying attacks. And when you aren't fighting, you're strolling along flat, uninspired levels with only the occasional platform or elevation to make it look like they made an effort. I couldn't bear it long enough to see if there were any flying stages, as it took me five levels of absolutely misery just to see Whirlwind. Avoid.
NINTENDO ENTERTAINMENT SYSTEM
Actually a totally unrelated game, Iron Man and Vision are kidnapped by Mandarin, so Captain America and Hawkeye are dispatched across America to save them. Like the Game Gear version, this is a platformer, except it's actually decent and playable. Not a masterpiece of any sort, but it's at least tolerable and a bit more interesting than all those other generic NES platformers.
The sad thing about all of this is that there's no arcade perfect port. If you want to experience the game like it should be, you'll have to emulate it. Lame.