The crew! Both versions of it allow for replayability as you have different objectives every game. It is a trick taking game, so they might be a bit familiar with it due to other games like bridge. And it is cheap. Only thing that might take them a bit to get used to is that it is coop.

Another simple one would be take 6 (nimmt 6).

• Bohnanza is a good recommendation. It’s very easy to learn and doesn’t fall into the usual brackets of shedding or trick taking.
• Scout is my favorite combo shedding game (ie. you’re shedding multiple cards at once). The way you’re always either drawing or shedding keeps the play much more dynamic than in Daihinmin or the Great Dalmuti
• Frantic from GameFactory isn’t widely available but in the EU you can probably get it. UNO on steroids. More exciting special cards and you can play them against any player, not just the one following you.
• Tichu a team based trick taking game that has a lot of fans around here. I personally have never really taken to it. It’s fine but I don’t get the rabid fandom some have for it.
• The Crew is ridiculously difficult with 5 and cumbersome with 2. Would only recommend it in between. But there it is a very clever game.

Bohnanza is a modern classic.

Scout is supposed to be great.

Tichu is a bit more complex (and somewhat similar to Doppelkopf, which as I am just learning is apparently rather specific to Germany).

Arboretum is also nice, somewhat similar to Lost Cities.

We often play “6 nimmt” with our Grandma. That is always a blast. Simple to learn, quick to set up and a lot of Schadenfreude from my Grandma when she tricks somebody into taking cards!

Exploding Kittens is always a winner when I break it out.

I would also echo the Crew is great, especially for people that are familiar with traditional card games.