This is an incredibly subjective debate, thus nothing can really be determined.
That said, for me, the two are/can be very different. "Fun" means, basically, "did you enjoy it?", and it's absolutely possible to enjoy something that is objectively terrible (see: B-grade movies, schlock films, etc). Similarly, it's possible for a "good" experience (meaning well-crafted and executed, etc) to be blatantly not fun (see: Schindler's List, et al).
In the realm of video games, generally "good" is equivalent to "fun", simply because games aren't very, well, good at handling "not fun" subject matter. The only game I can think of that qualifies as "good" and "not fun" is Dear Esther, and that's mostly because there's very little actual game involved there.