I don't understand why people won't understand that Mario is both faster and stronger than Luigi! Luigi is able to jump higher and he's smarter! I suppose you want proof:
Speed: In Super Smash Bros., either the original or Melee, start a 2-player versus match. Both players (Mario and Luigi) should be human. Stick them at one end of the Great Fox, and make them sprint in the same direction. If Mario is in front of Luigi, they will gradually grow further and further apart. If Luigi is in front of Mario, however, they will stay together the whole time, since Mario has no trouble keeping up with his slower brother.
More direct proof on Speed: Play Super Mario Advance. If you look at Luigi's stats on the character select screen, he has 3 stars for speed. Mario has 4.
Strength: In Super Smash Bros. and its sequel, ALL of Mario's smash attacks are stronger than Luigi's. Now, you may say, "B-b-b-but Luigi... he has the stronger special techniques!" Yes, that may be true, but Mario could do just as strong attacks except he's not trying. Look at their faces. When Luigi does his Cyclone, he's sweating and giving it his all. His clumsiness, however, hinders him and he only hits twice. Mario, on the other hand, smiles the whole time while doing his Tornado, hardly expending any energy whatsoever. He hits 7-10 times. If he was trying his hardest, he would cause 49-150% damage per Tornado. Of course, that's probably why he isn't trying. If he was, he'd be invincible, thanks to that move. Also, on a more humorous note, in Melee, when Mario lands from a jump, he's rarin' to go, ready for action. Look at Luigi's face when he lands from a jump: Ow! My knee! This may be credited to the fact that Luigi jumps higher, however...
...But then again, maybe not.
More direct proof about Mario's superior strength: Play Super Mario Advance. If you look at Luigi's stats on the character select screen, he has 3 stars for strength. Mario has 4.
Luigi's Jumping Ability: Duh, play any Mario game that differentiates between the two characters. I don't think there's any argument as to who jumps higher.
Luigi's Intelligence: He's been the brainier brother since they actually gave him a personality on the cartoon. In the Mario Party Manual, it states that Luigi is smarter than his big brother (Hmmm... it also says Mario is stronger).
That is all. Thank you for your time.