I agree with @
Bryonato
's tier list for the most part. There is justification for Samus so high, great surviving and just wrecking up damage slowly but surely while getting less damage at the same time without getting comboed. People underestimate this because most are all out for as much combo + offense as possible, but Samus tilts+jab, her nair and missiles do the job. A good way to find how you can find out about how strong a character is is examining their neutral game and possible weaknesses/counter-strategies. While most characters are up there because of the neutral game, Samus is great because she has to commit barely and is strong at range, in close combat and doesn't get comboed (well not top tier because other things miss but still it makes her deserve the place).
Btw I think Mario is slightly worse than MK/Sheik/Falco/Wolf, range would be one reason, "floatiness", at least in comparison, makes him have to commit more and that weakens him. If I would have to give the spots in an definite order, it would be 2. Falco (lasers, i tend to rate neutral very high which I am sure should be the way to go because a slight neutral game advantage can be waited out with accumulating positional advantages / forcing opponents into options and will make you win it, if played well, almost every time, what can you do if you can't win neutral?), 3.MK (hm strange his neutral is the worst from MK/Sheik/Falco/Wolf but he has the ability to use mixups better than other characters which gives him always a clear probability to win neutral, in opposite to characters that will just lose it over time and have to wait for slow reactions/errors. The reason I give MK 3rd is his possibility to convert a positional advantage into damage while keeping the advantage with his incredible positioning, leading to long hitstrings which are not really combos or techchases). 4.Sheik 5. Wolf (Wolfs punish game is stronger but Wolfs lasers are his best neutral weapon because his aerials aren't good on shield and you can work around them while needles are just an incredible option devastating the opponents neutral game winning attempts)
I would also slightly downrate ZSS because of grab issues and resulting neutral game issues, but just a little bit because she has the strong punishes and can win neutral with her vertical aerial mobility (great tool for winning neutral, e.g. Wario has almost nothing else in neutral and this makes him decent), at least sometimes and neutral b also helps out.
Long post, I know, please read it anyways^^