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?
In what canon? There are so many different Mario story variations that it's hard to say. Overall I also prefer Luigi, but there are some stories where Mario is clearly superior.
NES games except Mario 2: I think that they are essentially equal. Your argument that player 2 gets to see what player 1 did first only holds true if player 1 stays ahead of player 2, which is not remotely guaranteed on those games. Luigi may be a personal preference here, but he's not better.
Mario 2: yes, Luigi is objectively better in most senses. The jump and so on. However, one could make an argument that Mario is a more advanced choice since he doesn't have those extra advantages. The same argument holds true for Super Mario 3D World. Mario is objectively harder to play with, which some would find superior.
In most of the 80s cartoons, Luigi was displayed as a bit on the cowardly side, whereas Mario was more take-charge. It's not as simple as that, but overall I would say Mario is superior here.
In the Valiant Comics story universe, Luigi is clearly superior in every way, though. This is my favorite mario universe, so hence my overall preference for Luigi. Luigi is pragmatic and does not seek recognition. Mario is reckless, frequently a bit stupid, and kind of mean at times.
In the comics from Nintendo Power in the early 90s, however, we see the worst of Luigi. He is practically a caricature. This unfortunately shows up in other later iterations as well, and in these universes it is no contest that Mario is better.
In a lot of the Mario sports games, there is either no substantial difference between the brothers in gameplay, or Mario is better. Generally BOTH of the brothers are used as the "average choice" for players who don't want someone more esoteric.
I could go on and on, but that's enough. My stipulation is that there is not one Luigi, but a multiverse of them. A few of them are objectively better. A lot of them are objectively worse. A fair number are down to option and preference. While I would love to completely agree with you since it's also my personal preference, I have to reject your premise.
EDIT: In the Mario "Nintendo Adventure Books" (choose your own adventure), the characters are very similar to those from the Valiant comics. However, Mario is a lot more reasonable there. In that universe the two come off as more equal, although Luigi is the one with a few more quirks and Mario is slightly more take-charge on balance.
Also, to your note about mustache superiority: it again depends on what you're referring to. Luigi's has grown more superior with time as Mario's has grown more mundane, it's true. But in a lot of the older comics and box art and so forth, Mario and Luigi either sported the same one or else Mario's was a bit better because of the proportions of his face. That's just my subjective opinion, but since you brought it up.