You heard me. Now's the time to wake up, sheeple. Today, I'm going to peel the wool from your eyes and reveal the truth--that Luigi is the better of the two Mario bros and he deserves our respect, trust, and dignity.
(1) Luigi is green. Have you seen that shade of green he rocks? That's some serious green right there. Green is a tranquil color. Green is often used to signify safety, ie 'green means go', or terror alert level green is the safest. Trees. Grass. Cucumbers. Nature. What is the color red? Warning. Stop. Danger. Blood. Communism. Nazism. Absolute chaos. Mario's primary color choice is the embodiment of fear underscored with a tonality of madness. Who's more likely to cut you off, a green station wagon or a red sports car? Point, Luigi.
(2) As player two, you can see the mistakes player one makes. Didn't realize there's a hole there? Maybe they missed a block. Hell, maybe they missed a pipe? Those who play Mario just plow along, unabated with interest to their surroundings. Luigi players are more observant. Careful.
(3) Luigi is quirkier in games. He can jump higher. He's got a cool headbutt move. He can do everything Mario can, only better. Mario, on the other hand, symbolizes normalcy. There is literally a trope called "The Mario", underscoring a character that is, on the whole, average in every conceivable way. Luigi breaks from that mold, finding a new way to stand out without going to great excess.
(4) Luigi is monogamous. He has had only one lover in his heart, Princess Daisy. Mario, on the other hand, is an insidious malcontent with a long string of lovers. Sure, you may remember Princess Peach, but what of Pauline? The woman from Donkey Kong? After she was rescued, she had been tossed under the bus outright, a mere pawn for Mario's rescuing-based sexual fetish. Hell, Mario still sees Pauline from time to time, but only of Donkey Kong is involved (and minis, for some reason). And remember Daisy from earlier? Yeah, she's from the Super Mario Land series on the Game Boy. This means that Mario went from Pauline, to Peach aka Toadstool, to Daisy, then back to Peach! Luckily, Luigi was their to pick up the pieces after Mario broke Daisy's heart and showed her what a real man looked like. That's how it has remained ever since.
(5) Luigi has the better mustache. Go ahead and GIS it right now. Compare and contract the different mustaches. Luigi's is a fine affair, torn straight from the pages of yesteryear, invoking that turn-of-the-century ideas of being a strong, stalwart gentleman. Mario's mustache looks like a curtain and invokes that feeling of a seedy bastard leaving a 1970s porno theater.
(6) Luigi has the better personality. Strictly speaking, he actually has a personality. He can come off as a bit scared at times, but I remember a quote saying that true bravery is knowing your fear and overcoming it for the sake of a greater good. This is Luigi in a nutshell. He realizes his life is finite, but he knows what is to be done. Mario recklessly strides into the darkest depths of infinity. Mario is not brave. Mario is at the least fool-hearty and at its extremes suicidal!
(7) Luigi is taller. I know you are chomping at the bit, ready to call me 'height-ist' or whatever, but hear me out. Even if we can exclude all previously listed elements and all else was constant, we know that Luigi is taller. He can reach a higher shelves. He's got a longer stride. You can call me what you what, but at the end of the day, who are you going to ask to get that jar of pickles from the top shelf?
And I haven't even begin explore all options, here! He is not the Green Mario you make him out to be. Mario is, in fact, the Red Luigi. Now, merely try to CMV.
EDIT: I really did not expect this much response to something so trivial. I want to thank you all for your participation today and you are, of course, welcome to argue in my absence.
As for me, Luigi will be my favorite, literally forever. That bitch got me Reddit Gold! That is literally blowing my mind.
However, I do subscribe to the multiverse Luigi theory now, so.. Point somewhat changed?