If Germans say they are planning on having a 'gemütlicher Abend', it usually means that they will spend it by themselves. If it is with friends, that's usually specified ('mit Freunden'). I have never heard of anybody having a 'gemütlicher Abend' in a bar etc. Public places can be 'gemütlich' but that has nothing to do with 'Geselligkeit' but with the atmosphere of the place.
If you check the Duden, you will find that Geselligkeit is just one possible aspect of Gemütlichkeit.