The best games in the world have amazing gameplay that challenges gamers to devise new strategies to defeat their opponents. They also give you dozens of ways to complete a single objective. A great example of this has to be Witcher 3, where you can take out enemies with melee weapons,spells, potions, track down enemies using your senses, and you can even bewitch people and bribe them. It makes playing Witcher 3 so much more exciting knowing that you have so many options to choose from. Not to mention the quests in this game are unique and extremely well crafted, you don't get a ton of repetitive quests asking you to go and kill someone or collect an object. There are only two things that are repeated and they are contracts and quests to find armor pieces, both are optional and both change slightly each time.
But coming back to my original point that gameplay is important, you only have to compare Witcher 3 to Dragon Age Inquisition's immensely boring world to realise how important it is to be able to choose the way you complete your objectives, and the way you fight each battle. Doing the same thing over and over again can get old very quickly.