I've been making forums for 7 years now, and it really depends on what you're looking for nowadays. If you're looking for a community to talk to, become one with, etc. Forums, and other form of groups like forums are still the best place to go, however, if you're looking for exposure, and quick views/replies, then social media is the way to go. Forums offer a lot more than social media, such as a growing bond with one another, and the ability to communicate on a more efficient scale in my eyes than social media. Yes, social media is rising, and it is costing some activity, it won't ever replace forums. The biggest games, websites, etc. have their own forums still. Any gaming website, or game itself has a forum for it that is extremely active, and well used. There are social media groups for this, and hashtags, etc. however, they are still not as efficient as forums in many ways. When looking for a group, it's hard to go onto social media and try finding people willing to group up and play a game with. You can join a facebook group, and post in it, but I see facebook more as a self promotion place than anything. Everytime I join a group on facebook it's always filled with spam, links, and self promotion. Twitter is all personal with hashtags to get other bots, etc. to re-tweet you and to gain followers. From my experience most social media is just for advertising. This might be because of the fact that I use social media for promotion, and it's what I generally look for when on social media, however, no matter where I go on the social media platforms, all I find is ads.
TL:DR I personally think forums have a stronger bond, and social media is mainly self promotion type of use.