What does a Spiel game refer to?
If you want the ultimate depth:ruleset ratio, come learn Go :) Every game is so different and exciting
Spiel des Jahres (Game of the Year) is a boardgame award that notably favors family-friendly accessibility. If you're seeing the award on the box, you can be confident that even if the strategy can potentially get really deep, you can still break this out to have a fun time with both grandma and your 12 year old cousin.
Spiel Des Jahres is a prize they give every year to a bunch of board games. Don't look at very old board games, but some of the modern ones: https://en.wikipedia.org/wiki/Spiel_des_Jahres
As for Go, I was tempted, but it's also very abstract, I do like some kind of theme in my board games.
A board game well integrated with the theme gives great vibes.
Some of the games great from there: - Sky Team, discovered right there on the wikipedia page: for 2 players, me and my wife spent countless hours on it. Very simple rules yet so damn fun - Azul up to 4, simple rules and a lot of depths. Place tiles on a board while stealing from others the stuff they want to use - Kingdomino is so simple yet choosing the piece (some form of draft) requires thinking ahead so many turns! - Dominion is still a great game: deck builder with simple rules. Didn't think that was possible? It is!
A lot of the children games are also great (this is for families with kids)
Some nominated are also great, even if they didn't win