This app was mentioned in 9 comments, with an average of 1.11 upvotes
Card Shark: https://play.google.com/store/apps/details?id=com.easy8.cardshark
It is not free, but there is a Lite version too.
CardShark is quite good too. It's got a huge collection of variants - like 40+.
I like classic games, maybe you will too.
CardShark - By far the best classic card game collection. No ads, graphics and movement of the cards are nice, customizable, just perfect.
Enjoy Sudoku - A proper sudoku app to teach you different techniques, great for both newbies and competitive solvers.
Sporcle - Popular trivia website with an app. The app is decent, I usually play on science, geography, music and literature categories. Haven't tried other trivia games and I'm a bit biased towards it. Don't mind the negative reviews, the app is working very well, the only complaint I have about it is that in geography categories, the map quizzes don't show the map, but you have the challenge already written for you.
Board games - my second favourite genre
Exploding Kittens - Discovered it when I asked here for games to play with my fiancee. You can also play with the AI or online, the servers are usually busy and you'll have no problem finding someone to play with. Has IAPs to buy different decks but they're cheap and well worth it.
Other popular board games I play in physical version but have pretty good android adaptations - Patchwork, Carcassone, Monopoly and Ticket to Ride. Haven't tried any others.
Hope I helped.
CardShark is quite good - https://play.google.com/store/apps/details?id=com.easy8.cardshark
Card Shark (solitaire) https://play.google.com/store/apps/details?id=com.easy8.cardshark
Gemistry (and other similar games by Hohng) https://play.google.com/store/apps/details?id=com.TheHohngCompany.Gemistry
Match-3 Jewels https://play.google.com/store/apps/details?id=com.hectopixel.match3
Mahjong https://play.google.com/store/apps/details?id=com.anhuimahjongfree
Classic Words Plus (like Scrabble, but Scrabble app is awful) https://play.google.com/store/apps/details?id=com.lulo.scrabble.classicwordsplus
CrossCraze Pro (also like Scrabble) https://play.google.com/store/apps/details?id=com.ortsoftware.crosscrazePro
If there are other types of games you think your Dad might like, please let me know; I have many.
There's a lot of options for card games. Assuming you're not looking for just classic card games from a standard 52-card deck (in which case CardShark has you covered), there's a few different genres to pick from.
First is your ever-popular CCG titles, which include games like Hearthstone, Eternal, and Mythgard. There's a ton out there, so if that's what you're interested in, I know there's a bunch of threads on those specifically with people having it out about their favorites.
Next are your roguelike deck builders. Games like the soon-to-be mobile port of Slay the Spire. Some current popular titles include Meteorfall, Night of the Full Moon, Pirates Outlaws, and Rogue Adventures.
Then there are your proper tabletop deck builders, games like Ascension, Star Realms, and Shards of Infinity. Ascension and Star Realms are both free for the base game, and are both excellent titles. Shards of Infinity is great as well, but is newer and more lacking in content, but the AI is arguably stronger if you're more focused on single player.
Then there's the big daddy of physical-turned-digital tabletop games called Race for the Galaxy, which is a lovely (albeit clunky) tabletop game that is transformed into absolute perfection in its digital format, and with a ludicrously strong AI to boot. One of the /r/digitaltabletop community favorites, and what many other digital titles are ultimately compared to in terms of quality.
Then there's a huge assortment of card-based tabletop games with a lot more depth, such as Through the Ages. It's basically a civilization game played with cards. If games like that fancy you, head over to /r/digitaltabletop and there will be a lot of posts going over those.
As for my favorite? Ascension or Race for the Galaxy. The former offers ultimately more content if you buy the DLC/IAP and gets the majority of my time, the latter offers an incredible challenge and a lot of thinking/depth.
Card Shark has both games as well as many others, pretty good AI
https://play.google.com/store/apps/details?id=com.easy8.cardshark
I thinks it's single-player only.
Yes yes! I was thinking this. The closest app is https://play.google.com/store/apps/details?id=com.easy8.cardshark&hl=en. You cannot create any games but the app itself is versatile.