It depends on which friends these were - and (very much) who the GM was. Some people can make a crap system just sing, or are just good enough GMs that their awesomeness outshines a hated system (I'm lucky, I've gamed with some REALLY good GMs over the years and have had the honor of calling many of them friends). Aside from that, there are of course some friends that I'll go to an insurance seminar with, so yeah, I'll play whatever with them.
And some, I just won't. I note, for the record, that the ones I will game with regardless do tend to be people that aren't 'gamers' per se, so much as 'people who game.' Not making anything out of this, it's just an observation made whilest thinking about it.