Honestly the super wario bros type thing sounds really cool. I've never really liked either walugi or wario much but that would defiantly be cool.

I personally think an awesome game would be a open world game sort of like a mixture between last of us and skyrim in gameplay set in an apocalyptic world where the water levels raised and there's just about no solid land anywhere kinda like that movie that
I can't remember the name of. It would also be part sandbox game in which you could create your own boat/raft type thing from piece of garbage you plunder from others or find around the world. There would also be floating bases or trading posts where you could buy stuff and trade treasures. Like the movie there would also be mutants but this would be an intentional thing that you could induce by eating special foods or something, the mutations would help you survive on your own but the more mutated you are the less likely people will want to interact with you.

Another idea would be a Frankenstein type game where you can take parts from fallen enemies and attach them onto yourself giving you varying stats rather then using armour. You'd also be able to progress through three skill trees named Mother, Father and Monster. Mother skill tree would focus on using electricity type powers such as stunning enemies or setting off electrical devices and things of that nature. The Father skill tree would involve more defensive type things such as better part drops off of enemies, more durable parts and being able to blend into crowds better, basically the route for the stealthy character. Finally the Monster tree would focus on normal warfare such as powerful punches and weapon proficiency and leading up to being able to leap huge distances, throw enemies at each other or even being able to do massive, destructive ground pounds.

Also as much as I like lots of story in a game (in fact I LOVE story in video games) I find fun games to be the ones that focus less on story and more on gameplay and mechanics.