I disagree completely, CaH is great the first few times you play it but quickly gets boring once the shock factor wears off.
The point is that it is an excellent gateway game and the fun amplifies the more drunk you become. I can play Card against Humanity with the people I would NEVER EVER EVER get to sit down in front of a board game.
I can play it down the pub or at a party, at Christmas and even with total strangers.
There are next to no games that provide that level of reach and because of this I use it as a hook/gateway to teaching newbies that modern games don't have to play like Monopoly and Trivial Pursuit.
My list is based on games that are awesome and that appeal to larger varieties of people.
Most people wont go near Terra Mystica, Imperial Assault, Caverna or Android:Netrunner, but these are some of the best games out there.
kaptainmarc wanted essential games and I feel that the games I recommended are modern classics because of the appeal to non geeks, appeal to both genders bias in tastes, offer a variety of game mechanics, most have decent immersion just not so much as to scare off the non geeks
- 7 Wonders
A great card game with massive appeal to a variety of people (both male and female non geeks)
- Dixxit
A game about using your 'left side' brain that appeals to artsy types or people who are less interested in logic, it also opens up great conversations
- Coup
A quick travel game that has bluffing and some great moments, but it is quick to teach and easy to play, so it grabs people
- Hanabi
A great game for flipping games on their heads, it requires communication and like coup is great for travelling, so it has the party appeal. It is teachable in just over a minute.
- Pandemic
Just an awesome co-op game which appeals to everyone. I have even played this with my parents.
- Forbidden Desert
A simpler version of pandemic if you like, but because if this it is easy to teach and like pandemic it is a game for people who don't like confrontation
- Robinson Crusoe
Just an awesome game because it is co-op, has mass appeal and is HARD, so people get involved.
- Splendor
Simple, quick to teach, but so enjoyable and even kids stand a chance of winning against adults.
- Cards against Humanity
As mentioned
- The Resistance: Avalon
Bluffing, deduction and co-operation, it is a great party game and the story is so well known and non gender bias that people will not get turned off by the idea
- Dead of Winter
I prefer it to Robinson Crusoe and zombies obviously have a larger appeal, it is basically Robinson Crusoe hardness, Pandemic appeal and has a deduction and traitor mechanic like The Resistance, so I couldn't really not recommend it.
- Cosmic Encounter
This game has been around since 1977.... that is 38 freaking years, it is already the classic that you haven't heard of!
I could have added Caverna/Agicula or anything by Stefan Feld because they are the modern Euro, but I personally thing the above gives range of style, depth of mechanics and audience reach.