Sunman was originally a Superman game until Sunsoft lost the licensing. To data, there are two prototypes. One contains one level with Superman as a playable character, and the other is a much more complete game with the new super hero, Sunman. Despite Sunsoft having their name all over this game, EIM actually developed this game judging by the credits.
The gameplay is very similar to Batman for the NES. You can walk, jump, and punch just like Batman. Sunman overall has slippery controls but at least Sunman can fly. The game is pretty hard.
The graphics on the other hand, are very nice. They are bright, colorful and detailed.
The music sounds quite bad. It's mostly the instruments that ruin potentially of great tracks.
Sunman is an alright game. Definitely not as good as Batman, but it's worth checking out.

This hack is titled only "Superman", pretending to be the official game and not the mediocre one of Kemco (the main character only needs a skateboard to be Dr. Slump version).

It's based on Pacnsacdave's hack "Superman 2 - Lex Luthor Edition" (all the credit for him), but includes important changes:

-Intro and title screen are replaced. Now the enemy to beat is Darkseid.

-Final boss sprites are replaced.

-Many generic thugs are replaced too for enemies from the comic-books, like the Parademon troops, Metallo or Doomsday.

-Minor changes on text to contextualize the new Nemesis on the game.

Note: Apply patch over the pre-patched Superman 2 - Lex Luthor Edition ROM.

No-Intro Name: Sunman (Europe) (Proto)
No-Intro version 20130731-235630
File SHA-1: 326E2F4D3BE11A9CD8E7A0C8DC345BA9ECC7D1A9
ROM SHA-1: A3791FE7928E8057E478F8D21B51B51C942325F5
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ROM prepatched with Superman 2 - Lex Luthor Edition
File SHA-1: 2AED3F7F3C9F81413EC1DF9D83826A55857267A7
ROM SHA-1: 1B9F5592FFC2C3ECC857A723E70298EEBDD07143