Terraria seems to be an epic hybrid of Minecraft and Cave Story. Terraria is a game where you have to look for resources before nighttime, or else you will die.
This game is great because it has potions,mana,fun combat, pvp, partys, NPCS, ability to sell, awsome exploration. Unfortunately this game tends to get boring really quickly when you seem to have the best "armor" in the game, which is molton, or if you have all the accessories in the game or all molton tools. Its a shame because Terraria has great mechanics in-game, smooth gameplay and awesome multiplayer (thats what really made this game better in terms of replay).
So if your looking for a fun 2D game that has Adventure, Action and Multiplayer then this is the #1 game choice for you.
Also as a side note, this game has EPIC BOSSES!!!