Recs.
Updated
Terraria is a 2D sandbox survival adventure game. The gameplay is centered around exploring a randomly generated world, while building structures, equipment and weapons from farmed resources. A survival game at heart, with a sandbox base.
SpecsUpdate
Pros
Pro Progress consists of world state and tradable items
Character advancement is only gear upgrades and increasing HP and MP with consumable items, so one player can craft/collect and share everything. The world advances with event triggers, and doesn't depend on any individual character.
Pro Intriguing world
Terraria uses a bright color palette and an upbeat chiptune soundtrack to ease you into its world. However, once you start exploring and spend time in it you'll notice it's not as cozy as it first seemed to be. Blood Moons that rouse the dead from their graves. Goblin armies trying to destroy everything in their wake. Vast and dark cave systems, filled with odd creatures and various dangers. Ancient ruins, teeming with the restless dead and evil spirits. Pockets of decaying land, thriving with misshapen monstrosities. It's really fun to explore and discover something new about the world of Terraria.
Pro Playing with friends allows for endless scenarios
Up to 8 players can join any Terraria world. You can progress through the game normally, build a race course and compete in it, or split into factions and wage war against each other. The scenarios are endless, you just have to let loose your creativity.
Cons
Con Low replay value for those who play it as an adventure game
Terraria is a sandbox platform-adventure game, so it partly hinges on beating various bosses. If you play it purely for the sake of defeating all the bosses, you might have little else to do afterwards. Restarting the game won't be as enjoyable either because you'll already know what to expect, causing continued play without a new goal feel mundane or boring.