Definitely Legend of Zelda because the game actually ends at some point. However the games can be very confusing when you get to certain dungeons. If you use a walkthrough you'll be fine. LOL will take a lot of time away from you, especially since it's an MMO.
Play League of Legends. It's a lot more fun than the Legend of Zelda and it's also multiplayer. But, if you really don't have the time to play a 45-minute game without leaving, then play the Legend of Zelda.