Because popularity / recency is a big topic right now, I thought I should list some characters who were really recent / unheard of at the time.
Smash 64 (1999):
and
both were introduced in 1996.
Fun Fact. In Europe, Pokémon Red and Blue and Super Smash Bros. came out 3 months apart from one another.
Also,
and
were unheard of for the most part.
Melee (2001):
was introduced in late 1999.
(Once again in Europe, Smash Bros and Pokémon Gold and Silver came out a few months away from one another)
has only been in one canonical Zelda game, being Ocarina of Time in 1998.
has only been in one canonical Zelda game, being Ocarina of Time in 1998 and Majora's Mask in 2000.
and
hadn't been in an original game for over 10 years.
hadn't existed yet.
Brawl (2008):
was introduced in 2005.
was introduced in 2006.
(Europe once again got Pokémon Diamond and Pearl 11 months before Brawl. It's a little better but jeez, step up ur game Europe)
was only in a Japan-only GBA game that came out in 2006.
hasn't been seen in an original game for over 10 years, similarly to
+
.
has never been in video game. (That wasn't a cameo or spinoff, mind you)
has been on Playstation consoles more than Nintendo consoles.
Genesis does what Nintendon't
Smash 4 (2014):
was introduced in October of 2013. I know he was chosen before XY released, but still. (At least Europe didn't get their Pokemon and Smash games at the same time, later than everyone else)
were all introduced in 2012.
Duck Hunt Dog hasn't been in a game for over 30 years now.
was introduced in 2007, and has only been in 3 "traditional" Mario games.
was introduced in 2010, and wasn't brought over to North America until 2012.
has only been in two games, and isn't popular.
TL;DR: Popularity and recency aren't really that important of a topic, because every Smash game has had those oddballs strewn about.
I know this is just the tip of the iceberg and it's highly opinionated, but it doesn't take away from the fact that Smash Bros. doesn't always choose fan-favorites. If it did, we'd have King K. Rool, Ridley, and Mewtwo by now.