Of course, gameplay is the most important part but I think that's different from the "fun/entertaining" subject. I personally want games that rely much more on systems with good gameplay that allow for interesting subjects to explore that wouldn't be considered "fun".
Might be that the word "fun" means different things to everyone. But for example Minecraft, I love that game but most of the things you need to do can be very frustrating, take alot of time and at times hard, so not very "fun" but very highly entertaining and here it's all systems and freedom,
Another example would be Morrowind, many would argue it isn't very fun, well at least back in the day I heard that often, in that it is very open and can be very frustrating in it's lack of clarity and often ending up in impossible situation, but it is also one of my favorite games!