Super Clash Bros is another arena fighting game with characters from many retro games. Author claims that he is gonna add over 70 characters to the game. But the game will also have level progress adventure mode. So basically you can pick character and play the game of the other character. Like you take Scorpion from Mortal Kombat and play Sonic The Hedgehog levels.
The game is in development and nobody knows when it will be finished. Maybe in several years. You can try the demo here: https://gamejolt.com/games/super-clash-bros/336304
The author of the game created a topic by himself on the forum. So you can ask him anything: http://theguardianlegend.com/forum/index.php/topic,2072.0.html