I've put a solid 500 hours into terraria, and it feels like I've only scratched the bottom of what the game has to offer in many ways. I've not managed to get close to killing the biggest bosses the game has to offer, or making the greatest items. I haven't installed a mod yet, although I've thought about it quite a bit, there are a lot of mods out there apparently. Its honestly hard to think of another game that still has this level of replayability after I've already spent this much time enjoying it. The graphics are charming, the difficulty is reasonable, and the complexity is just right.