Gonna concur with the above suggestion - from what you've looked at, Munchkin seems like the best fit. King of Tokyo and Boss Monster are more complex than they appear, and they can bog down a bit.
If you want some other suggestions for "simple to play" that are still certifiable hits, consider these (ordered from simplest to less simple):
Love Letter: It's a game about trying to guess other people's cards and playing cards to take special actions. The entire game is just 18 cards, but it makes for a good amount of fun for new gamers.
Splendor: Simple, addictive gameplay where you're trying to balance your turns between picking up chips to buy cards, or buying cards that give you discounts on future cards.
Hanabi: Deduction/logic co-op game where you all try to play cards together into specific sequences - but the twist is that you can't see your own cards, and have to clue each other on what you're holding, and hope you play the right one.
Machi Koro: Roll dice and build up your little "town" to reap as much reward from different dice results. Neat, colorful graphics and a good mix of gameplay between classics Catan and Dominion (two bigger, more complex games)
Ra: This one is like Sushi Go in that you collect sets of things to score points, but rather than pass cards around, you win the items by an interesting auction system.