Agreed on the point that Smash 4's roster feels very up-to-date. I think a lot of that has to do with the fact that lots of these series have upcoming games (Yoshi's Island, Star Fox, Street Fighter, plus all the obvious ones like Mario or Zelda) Nintendo also did a generally much better job managing their series between Brawl and Smash 4 than between Melee and Brawl (reviving Punch-Out and Kid Icarus, saving Donkey Kong Country from spinoff hell, etc.).
Could you expand a little bit on Brawl's roster feeling outdated? I'm inclined to agree but I'm sure you can think of more examples than I can.
I'd like to chip in saying that when Brawl was released, even in Japan we already had Super Mario Galaxy and Fire Emblem: Radiant Dawn. There was practically no mention of Galaxy in Brawl, and Ike used his Path of Radiance design from 2005. Of course, this had to do with the game's roster probably being finalized before the Wii was released, and no doubt Sakurai had slimmer pickings back then. After all, Rosalina hadn't proved herself yet and he had already eliminated later newcomers like Villager and the Mii Fighters.
Given the emphasis of newcomers from veteran series (Dedede and MK, Lucario and Pokemon Trainer, Diddy Kong, Ike, Lucas, Zero Suit Samus, and Wolf versus ROB, Pit, Olimar and the third parties repping new series) with nobody debuting from a game later than '05 you've got some kind of argument for Brawl's roster feeling outdated.
Then we look at Sm4sh's roster featuring the following characters repping a new series:
- Villager (Animal Crossing)
- Wii Fit Trainer (Wii Fit)
- Mega Man (Mega Man)
- Little Mac (Punch-Out!!)
- Shulk (Xenoblade)
- PAC-MAN (PAC-MAN)
- Duck Hunt (Duck Hunt)
And that's not including newcomers from veteran series that came from recent games (Greninja, Dark Pit, Robin and Lucina, Bowser Jr. [Sunshine is recent right lol], Rosalina and Luma) and Ryu from Street Fighter, a DLC third-party character. Of course, this time there are far more options and no doubt Namco Bandai's help probably lead to some of these inclusions. Then, thanks to the Woolly World stage and references to still-current games like Splatoon, it all keeps Sm4sh feeling modern for probably the rest of the 3DS and Wii U's lifespans.
tl;dr I want Wolf as DLC and will willingly pay $7 for him and a stage consisting of Sakurai shitting on the faces of Ridley fans.
Edit: I just learned that 8-player FE!Roy matches drop the frame rate ever so slightly, to like 50 something.
