Popular in America forever perhaps, but even then, in the years between Brawl and now, Japan has started warming up to the idea of Ridley playable alot more than what it was, as he's even now reaching the Top 10s of their most wanted polls, and Metroid isn't even that popular in Japan...that's how popular Ridley is, and it personally makes me smile.
As for the trend of a Starfox character a game, that's possibly a trend, but even then, during that time, the franchise had games come out between each Smash game, Starfox has only had a 3DS remake (Which people are too hopped up on Nostalgia to let go of the old VAs and how bad they were) and that's it. Krystal hasn't appeared in a game since Command, which was before Brawl. Wolf was an obvious choice though, and I don't think it's a trend that made Sakurai pick Wolf to be playable in Brawl, especially when alot of people argue that it was Wolf that should have been playable in Melee instead of Falco.
