Factorio

Factorio is about the automation of production lines and logistics puzzles, and it does it amazingly well. If you enjoy those mechanics then it's going to be easy to lose a lot of hours to this. I personally think it's easy to pick up, but it's one of the deepest games I've ever played and it can take hundreds of hours to get really good at. It's extremely satisfying to automate the production of something complicated. The tools it gives you to manage these puzzles are really well designed, mechancically, and the gameplay loop is really rewarding. It's spoiled me really - I've reached almost 500 hours in this now and it makes all other games feel shallow and short in comparison.

Pros [updated Feb 2023]

Excellent and lengthy tutorial
Background music that still isn't boring after 400 hours
Very relaxing, and addictive for people who like base building and problem solving
Built in mod support
Can disable the enemies and make resources infinite through in-game options if you want
Can deconstruct everything with no loss of resources
Enormous tech tree
Can copy/paste recipes from one machine to another
Has a blueprint system for creating multiples of building setups
Personal construction & logistics robots
Incredibly well balanced gameplay
Huge choice of how to play. You can turn the enemies off, or play with them on, or use a preset map, and change all the options you like
Rewarding gameplay loop
Probably the best inventory system in a game. Auto-sort, robots to bring you things and take stuff away, toggle switches for personal inventory management etc
Effecively infinite map, so you can expand for as long as you like
Huge amount of content
Beautiful animations on machines
No slow down, even with HUGE factories
I highly recommend playing with mods after you're used to the game. Playing Krastorio2 adds new recipies, rebalances old ones, adds extra tech levels etc.
I originally hated the biters, but I've learned that they're a core part of the game mechanics. Yes they're annoying, but they're also deeply tied into the pollution mechanic in a way that makes you think more about how you build

Cons

Mods disable achievements, even if you're only playing with "quality of life" addons like better car handling
Biter mechanics are not really explained to the player, like how they spread, what happens when you destroy nests etc. My first base was swarmed with 50 biters within the first 10 minutes of the game before I'd even researched one technology and I had no idea why. You have to look this up online. Once I understood pollution, biters made a lot more sense.
You can't delete items, unless you put them in a chest and blow it up
I was pretty annoyed that it only showed me the popup for how to copy/paste buildings after 50 hours
It's not explained that oil fields "run out". It looks like they're infinite, then just as I was nearing the end of the base game I noticed my oil field production had dropped to 26%