Snake is not the best character in the game, I already described why MK is a better overall character than Snake a few posts back.
This thread should be closed, it's clear that MK is better than Snake. You can argue over just how much better MK is than Snake, but that would be a different discussion in itself.
Snake's moves are both powerful and quick, he doesn't have to be committed to a certain move when he can jab cancel into f-tilts, and he can choose to f-tilt once if he thinks his opponent will block the second hit. Snake has single move combos... you press 1 command button, and you put 20-30% damage from that one move with multi hit moves like N-air, D-air, and F-tilt.
You say Snake gets put into a very bad position when he is in the air... he can C4 drop to cover himself and air dodge safely, sure if Snake couldn't air dodge then he would be screwed. His up+B doesnt even put him in a helpless state after use when everyone of MK's specials does.
As for match ups...
Snakes match up mostly made of hardcore **** matchups. He beats alot of characters badly, he does have his counters, but even then the match is still winnable. These counter characters are.
Dedede (chaingrabs and waddle dees)
Falco (chaingrabs, spike, lasers)
Zero Suit Samus (ranged attacks, down+B, downsmash combo)
Diddy Kong (Bananas, side b gimps snake's recovery)
Donkey Kong (ranged attacks, spikes, cargo grab+stagespike)
ROB (lasers and gyro, high priority attacks, can outcamp Snake)
Wolf (d-throw by edge+D-air spike, laser spam)
Olimar (outcamps Snake, and has a useful spike against Snakes recovery)
Metaknight does have counters, backed up by tournament results, self experience, watching videos. Metaknight does beat many characters, but not as hard as Snake. His counters are.
Lucario (D-air ***** MK, and outranges MK.)
Yoshi (Chain grab release, invulnerable to shuttle loop edgeguard while double jumping)
Zero Suit Samus (Down+B beats all of MK's best moves, outranges MK.)
Snake (Grenades shuts down MK's tornado use. Outranges MK and outlives him)
Donkey Kong (Outranges, outpowers and outlives MK.)
Bowser (Chain grab release, outlives and out powers MK)
People would like to say MK has no counters cause most of these characters that do counter MK are very underused.
Also, just because MK has better matchups against the cast doesn't mean he is the best character. Snakes hardcore **** match ups are what give him the edge against the rest.
In other words...
Snake has more "QUALITY" match ups in his favor.
Metaknight has more "QUANTITY" match ups in his favor.