I really can’t be bothered with other Crypto Forums unless a pretty good reason crops up to ponder them over Bitcointalk. Even so, I’ve taken a quick glimpse at the list (so my first impressions may be wrong):


Bitalk.org                             -> Seems to be Russian only.
Bitcoin.com                          -> Not too active (not bad UI).
litecointalk.io                        -> Not really interested in a Litecoin specific forum + rather inactive.
cryptocurrencytalk.com         -> Rather innactive on substantial threads (like the video section).
bitcoingarden.org/forum/      -> Very similar UI (SMF). Structure a bit weird, and 24K members only.
bitcoinforum.com                 -> Also very similar UI (SMF). Not very active, and just under 18K members only.
allcryptotalk.com                  -> Not many boards not activity.
cryptorum.com/forums/        -> Very weak in terms of boards and content.
talk.peercoin.net                  -> Specific to peercoin
mastersofcrypto.com/forum/ -> I like the guides .. but nothing else (+ barely any activity).

So, in summary, none of the above come even close to Bitcointalk neither in terms of content nor, very likely, prestige and history of its members.