League is probably my favorite game of all time, I've been playing this game since I was 14 in my freshmen year of high school. While there is some skill to it, the game is primarily a thinking RTS(real time strategy) game that requires a refined thought process. Of course any game is simple, but to get a better idea of it, check out this video!
Dark Souls is hands down the most challenging game I have ever had the pleasure of beating, the creators pride themselves on the philosphy of "trial by fire." Which basically boils down to, there are no tutorials or guides to help you along your way, bosses and enemies are designed to kill you no matter what, and there is no difficulty selection for the game. When you play, you play on the creators terms. Some have argued that the game is too hard for some, but those who cant beat it are just unworthy. This game requires you to spend time playing it to the fullest, that way you can get the best experience from the game. To beat this game is essentially a right of passage in the gaming community.
There are 57 different games under the title Final Fantasy, however each game is a different adventure all together and typically does not follow one story line. What this series such an amazing ride is that the creators make such emotionally captivating scenes that move you with both musical score, and fully immersive story telling. An interesting theme that all of the games follow however, is that of deicide. Which means "the killer of a god", essentially in every game under Final Fantasy some evil villain attains god-hood of some sort; ultimately the villain is hell bent on bringing down the apocalypse