While Geno I don't know if I'd call Geno "final Brawl all-star", it is kinda clear he outlasted his contemporaries from the era that still aren't in the game in terms of maintaining popularity and discussion.
Takamaru hasn't really been discussed since he got AT'd. Starfy's series is in the ground and is thusly rarely heard of for Smash. Lyn has largely become a non-presence in speculation as her game gets older and the roster gets more modern Fire Emblem characters. Goroh and Krystal have both been tied down to assist trophies and haven't appeared since the mid 2000's and thusly have lost a lot of common support. Midna had a very brief resurgence thanks to Twilight Princess HD but quickly fell after that. Same deal with Skull Kid and the Loz leak. Paper Mario's still around and is seen as somewhat likely, but has lost a lot of his appeal among the core fanbase.
The only character that's really came close to keeping up with Geno in terms of fan demand from the era is Issac. Even then, Isaac has fallen on somewhat hard times thanks to Golden Sun effectively being dead and the contentious fact that he's an assist trophy. He's still pretty popular, but its hard to say he's really the juggernaut he was during Ultimate's pre-release.
Geno, similarly, kind of died after Brawl released. In fact, he died earlier than most of the characters previously mentioned, most of whom had some presence during Smash 4's pre-release. Where Geno benefitted was the fact he essentially came back from the dead, as his Mii Costume and Sakurai's statements showed that he wasn't quite the longshot that many thought he would be. That, combined with Ultimate's before-mentioned trend of giving massive fan favourites their due and the simple fact that people naturally like the character, allowed Geno to grow into the undeniable juggernaut he is right now.