So we added an Xbox One to our family game night. And here are a couple suggestions. Max: The Curse of Brotherhood will be GREAT for your 4-year-old. I played it with my 4 & 6 year old daughters when it came out & they still ask to play it every other week.
On top of that look into:
- Rayman Legends the 2nd player can't really die or negatively affect progress so it's a great game to play WITH your kid
- Child of Light another great game where you can play WITH your child. I played this with my oldest (the younger one watched & liked it too) and I would use the support character to keep her alive
- Lego Games always good family co-op
- Minecraft the kids go crazy over it
- Peggle 2 can't go wrong with Peggle
- Skylanders the games are fantastic; the caveat being it can get EXPENSIVE. I've managed this game by staying a generation behind & have had great luck getting figures for cheap
- Guacamelee co-op beat 'em up with good character
- PvZ: GW Plants vs Zombies FPS that you don't have to worry about the violence being gratuitous
- Chariot good co-op puzzle platformer
Terraria is perfect.
It is a 2d sidescroller like classic old Mario games, so it fits that description. But this also makes it easier for him to understand. Its also a Minecraft clone (which is another strong suggestion, as it is this generation's Mario) and provides dozens of hours of depth with item variations, mining, crafting, boss fights, etc... It also has up to 4 player splitscreen, so it can accommodate your whole family.
I have a 5 year old that is obsessed with it. He knows all the super complex recipes and gathering strategies. My 3 year old does well for himself. He can move and attack and he just likes going around and killing the bad guys. He'll hand me the controller if he gets stuck in a hole that is too deep to jump out of, as he doesn't know how to dig yet.