Hoplite is a great little game
The Lone Wolf Saga should need no introduction - way more than just a simple gamebook conversion
Punch Quest is a dumb endless runner but is actually really fun
God of Blades is a fun sword fighty game, but the real draw is the awesome bombastic 70s-prog Michael Moorcock atmosphere. Game oozes style
Tin Man Games have been putting out a lot of gamebook adaptations that are really fun, but
Sorcery! stands head and shoulders above the rest, for sheer effort put into it
Monument Valley is a fun MC Escher-esque puzzler with great art style
Fiz is a simulation about running your own brewery. Make and name beer and engage in bitter, hoppy rivalries!
Kairosoft games are all pretty good. They're weird little Japanese ports of very old mobile games, but they're all awesome simulator-lites that are
perfect for phone/tablet play. I like
Epic Astro Story
Wayward Souls, a Dark Souls-inspired roguelike. Just a very, very good game
Spaceteam if you have real-life friends
Organ Trail is easy to write off as an Oregon Trail parody but, shitty shooter minigames aside, it's actually a very compelling little OT-style game
Calculords, by 300-year-old internet funny person Seanbaby, is a weird mix of maths puzzles and other nerdery that I'm personally too stupid to be good at but seems like it could be good if ur into that kind of shit
Battleheart Legacy gets a good rep as a sort of Diablo clone or something I guess? Haven't played
Also a few classic-style dungeon crawlers that I've yet to try but get good reviews:
Deadly Dungeons,
Questlord,
Hack Slash Loot