Lords of the Fallen is an alright game but the world is significantly smaller than Dark Souls and it has a pretty poorly put together lore IMO. It isn't bad but it doesn't have that quality feel you get with a Souls game. The bosses are more generic, there's no multiplayer aspect, the world is more shallow, and you're restricted to the only protagonist who's name escapes me as he wasn't very intriguing to begin with. Dark Souls on the other hand will immerse you in some seriously well put together level design, hidden lore and real challenges. The variety of the game keeps it fresh as there's always a different path to take or a different weapon to try. There's just something about going from the campy feel of Firelink Shrine to the dark dreary depths of Blighttown that really make you feel like you're playing a massive game. All that said, both games are more challenging than your average single player RPG and will more than likely make you rage at one point or another. I personally think it's safe to say Dark Souls is the harder game, but much of that is due to the variety of boss fights and the length in comparison to LOTF. Tl;Dr: Lords was difficult and fun but forgettable. Dark Souls is fantastic, challenging and sure to set a standard for future games of the genre you play.