The best DK in the world is bum if you want to see the highest level of DK.
But nah DK definitely isn't a hard matchup for snake. Falco, Olimar, and Metaknight are, but not DK.
Falco's lazers limit the field of movement Snake has. If snake doesnt start each stock at 30% by blowing himself up, he can take up at 85% from CG to spike to c4 recovery. Falco can outcamp snake, and Falco's jab and ftilt are very good pokes on Snake. The
only problem falco has is killing, and it doesnt matter if falco can get snake to 200 just by shooting lazers and running away the whole fight. I''m taking this from tourney experience versus some of the best falcos on the East Coast, Keitaro and D1. It's much more annoying to fight falco than DK.
Olimar has ******** combos on snake, and olimar can severly outcamp snake horizontally. Olimar has no problem killing snake, and it's not that easy to edgeguard/edgehog a smart olimar. I'm taking this from my experience in tourney versus Blackwaltz, one of the best Olimars in the country, who has beaten players like Chillin in tourney. Much harder to fight Olimar than it is to fight DK.
Metaknight can easily overwhelm Snake. Mk's d-tilt outranges anything Snake has on the ground. It can combo into another d-tilt which most likely trips snake, and sets MK up to grab him and get him offstage. Mk's ftilt has insane priority, and in the air, MK dominates. Offstage, snake is as good as dead. Most of the time, snake will get gimped if he's offstage, and has little options to recover.
He can either:
1) come in with a nair and hope the mk messes up.
2) try to bait an up-b and airdodge
3) recover high with c4 and cypher
the problem with each of these is that at the highest level of play, the likelihood of these options working is slim. corresponding to each option is the risk of doing that option
1) at the highest level of play, the mk won't mess up
2) Mk can use Nair for the kill and it lasts longer than an airdodge
3) Mk can follow snake up high and kill with a ceiling tornado, which is hard to get out of
This means Snake cannot stand a chance in a head on fight.
He can camp grenades, but a smart MK can get inside and punish. How does MK get inside? By dashing in right? M2K has said "just do the first hit of the ftilt if they dash at you." and I asked Teh_spamerer, one of the best players out there, "what if they shield the ftilt?" and his response was "then go for a dash grab." Obviously, unless you can read minds or have played with that MK for long enough to know his habits, you have a 50-50 chance of being right.
My experience vs MK is gathered from countless matches with dmbrandon, teh_spamerer, inui, and a few matches with mew2king.
Mew2king says that Snake and Metaknight go even, similar to Marth and Fox in melee, and that it can depend on the stage. I agree with him on this, that for Snake, it's at best even or 55:45, but Snake doesn't win it.
And now, back to Donkey Kong. It's true that he can outrange snake, but his moves have such startup lag that you can see it coming and powershield easily. After the powershield, feel free to ftilt. DK can camp bairs; that's fine, but he's gonna land eventually, and snake and grab him out of that. Dk doesn't have an escape move like tornado or falco's side-b to get away from snake once snake gets inside to dk. and at long distance, all snake has to do is throw grenades at him. Just keep this up until you can land an up tilt and it's a win for snake. It's really nowhere near as difficult as people make it out to be.
I go by what I've seen or experienced myself in tournament. Obviously my word isn't law or whatever but I do know what I'm talking about for the most part. Hope this helps out a bit guys