And while Super Smash Bros. Ultimate is on the surface a simple fighting game. Once you unlock all 74 characters, special moves, spirits, etc. It's becomes a mind-bendingly massive combinatorial space!
braid was also pretty good
https://www.youtube.com/user/pannenkoek2012/videos
https://www.youtube.com/channel/UCYDnJiF0_RqSjkjvjRbG1tA/vid...
I suspect competitive Pokemon would probably be pretty intellectually stimulating too, if at the level of Smogon or the world championships. There are a crap ton of tactics in that series, and trying to anticipate your opponent's own strategies while countering with your own requires a lot of creativity and thought.
(Though I guess less popular ones can have interesting 'scenes' too. I'm on a Discord for Mario & Luigi series speedrunning, and titles like Superstar Saga, Dream Team and Paper Jam had a lot of neat discoveries as well).
Top players all have top tier mechanics and then it mostly comes down to tactics, the ability to metagame etc.
I personally enjoyed Dota in the past, for that reason, although I currently play games with smaller multiplayer sessions.
Or if youd prefer an existential crisis with your video game try the spectacular NieR Automata
Some of the total war games are good if you push yourself and don't glitch the AI.
Mapgames (Europa Universalis 4, Stellaris)
Rougelikes (e.x.: The original Rouge, Tales of Maj'Eyal, Nethack)
Zachtronics games as previously mentioned in the thread
Competitive?:
Dota 2
CounterStrike
Fighting Games (most)
Highly dependent on player count, but Starcraft Brood War and Age of Empires 2
If you really want intellectual stimulation then read a book.