It's always a treat to fight a well-designed boss in a video game, even if the challenge is pretty high in some cases. These climactic encounters force players to push themselves to their very limits and make for a great time, encouraging those brave enough to use everything they've learned to show these foes who's the real boss. It's rare enough to find mandatory story bosses that are all designed with great finesse, so it's easy to see why players would be more than willing to check out optional bosses that feature the same level of excellence in design.