I'll answer each.
"why is mario better than luigi? as far as i can tell, they are the same aside from dash attacks and specials, and luigi's dairs/uairs can end in an over-the-top kill while mario's can't."
Mario is better from luigi for 6 reasons.
1. Luigi's down air is very easy to DI out of compared to mario's.
2. Luigi has a much worse projectiles than mario
3. Luigi has a worse approach than mario.
4. Luigi is much easier to combo due to his high floatiness
5. Luigi has worse priority
6. Luigi has a worse dash grab and a worse shield pressure
This makes it so luigi has a wors ematchup vs top tiers. His main problem is his bad approach and bad priority. also, Mario's up smash kills just as well as the up b and is easier to combo into.
"Also what makes yoshi so good as to rate him above dk, luigi, samus, link? (well i can see link..)"
Even though the tier list is old...yoshi has multiple good properties
1. Yoshi's shield is broken....Yoshi is the only character with a powershield. If used perfectly, yoshi will almost never be hit.
2. Yoshi can use his double jump to cancel out of attacks.
3. Yoshi has a really good Double jump cancel which allows him to attack incredibly quickly
4. moderately good projectile
5. good approach outside a horrible grab.
6. a good recovery if used right
7. As said before, up tilt is broken, it combos into kills and 0 to deaths regardless of percentage.
The main reason why yoshi is not higher is due to the grab and the fact that yoshi has major problems with the top tiers. If yoshi had a better grab...and if he was easier to use, he would be a better character.
Also, by the way,