Ok imma try an Emblem Lord post:
Alright suckers, look at these facts.
Good mobility = good option coverage = controls the game better = wins more = wins because they outplayed (vs haracter or MU factors) = possibilities in all situations/gamestates/times.
You know when that is true?! ALL GAMES ALWAYS, SON!
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Seriously this applies to pretty much most games. I don't know much about 2d fighters so ill be quiet here, but shooters? Faster gun classes get used more, tf2 had pyros and heavies get phased out as scouts (who... move fast and have a double jump) got more skilled. They could just do more, cover more, be there when they needed...
RTS? First skill is building a strong army, then smashing someone as you both fail to control your army. But as the game matures, mobile armies ALWAYS become the meta. They can harass, hit you when the conflict favors them, pin you in your base, and run when they won't win.
Hell, chess? The best pieces control the most board, the fastest. Friggin checkers and a piece that can move backwards controls much more of the game than the low tier plastics that only move forward.
Hell, I believe in MegaMang because he has sick aerial mobility, and that is enough to corner anyone.
You know who doesn't have good air mobility? Diddy Kong. He is *trapped* by anyone below him with better airspeed AKA the entire cast nearly, so OF COURSE Zero MF's out of disadvantage constantly. Everyone is saying it is dumb but he has to do something, it is a good option frequently and it got him to game 10 of grand finals of a major vs Salem's bayonetta. But... he did get read. That MF was bad, and possibly a mistake anyways. But, there is a reason he does it, it isn't as horrible as everyone is saying
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So where does greninja fall? He is absolutely mobile. Both special and normal mobility; usually i'd say normal mobility is king but special movement has made big moves in this game, though bayo should be exploited more.
But as with the RTS analogy above, mobility is where you can HIT, and where you can BE HIT. Greninja has bad 'hitbox mobility', at least compared to shiek. I have learned this from shiek. The fact she can get that fair/nair in your face immediately is HUGE for what options she is covering/threatening. Greninja isn't as good here... But, he can just not get hit, not be in the situation, and engage when it is favorable. (Or, swing a fair where you can be, but where you cannot hit him, aka my whole greninja playstyle rofl), which really reminds me of Salem's bayonetta and may be why he thinks the character is the balls because guess what, he is more mobile than bayo, has more guaranteed combos, a sick projectile, lives longer (except vs gimpers/ironically bayo) and is in some ways more dangerous. Where will this get him? IDK. but,
Mobility is king. Remember this when you pick a gun/race/car/husband/wife. EDIT: RACE WAS REFERRING TO SC2, I REALIZED THAT NON SC2 PLAYERS MIGHT READ THIS WRONG, I APOLOGIZE. If you have the heavy gun and can move slow, you need support and you need to outsmart. If you have the scout/pistol, you can see the heavy gun and just... go shoot their medic. If you are greninja, you can leave, but you can't smack them f5 (though his jab is sick, blah blah cstick jabs while walking into fsmash is damn good)