Make your players happy, and they will deliver a great game.
Now, don't forget to challenge and frustrate them too. A GM must feel out his players, understand why they are there and what they want from the game, find a way to dangle what they want in front of them, make them jump through hoops to get it (very hard if a player absolutely refuses to jump through hoops), let them get REAL close, snatch it away, then (eventually) let them have it. Or die trying.
If your table is three to five players, meshing together a game and story that offers a chance to fufill player wants becomes the GM's real obstacle to providing a fun game. A plot that concentrates on one PC may cause dissent amongst the others. A PC who is near diametrically opposed the the rest of the party in values, tactics, approach, skill set: all can create an impossible situation for the GM. So a GM needs to learn to mesh and balance a party in order to be able to deliver a good gaming experience.