Sakurai should add another online mode for taunt parties or screwing around, because that can actually be fun.
He did. It's called "With Friends" mode! :V
Because honestly, screwing around in a game is not as fun without friends.
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I disagree with the notion that Smash 4 has "no chance" of having a more successful competitive scene than Melee. In actuality, it has an easier shot at being big, because of online play being an official thing, which will get people interested in local tournaments, especially if they participate in online ones. Plus there is the point of it being the most recent game and therefore being on the radar, AND it has two versions available (and people who play the 3DS version could still enter tournaments for the Wii U version, as their practice with the characters carries over due to the mechanics being the same). Also, a lot of big YouTube channels are going to have coverage of it (as long as they don't monetise the videos, they can still upload them).
Not only that, but while Brawl was overly defensive, Melee is overly offensive and it's advanced techniques are all obscure exploits or outright glitches that the game does not teach you about, meaning you have to research online just to find out that they exist and how they should be used.
Right now, Smash 4 is looking to be a fine balance between offensive/defensive play, and strategic/skill based play. This even looks to be the case in terms of roster decisions (Little Mac and Greninja will feel familiar to Melee players, Mega Man and Villager will feel familiar to Brawl players). If this holds true, it will objectively be the most accessible Smash game, and will mean people from all walks of life or the Smash community can have a fighting chance at being considered a good player (as they will choose a character that fits their play style the most, which I didn't really think you could do in Melee. Every character required you play offensively, so it felt more like I was picking variations of the same play style). This in turn, could mean that this game surpasses Melee in competitive popularity.
None of this is a sure thing, of course, but the game having "no chance" is not a sure thing either.