Halo wasn't the only reason, but it was a significant one. Unlike Wind Waker or Metroid Prime, Halo was a killer app that moved hardware, and helped give Xbox the edge they needed as a newcomer to the market to outsell the veteran Nintendo.

Their superior third party support was a factor as well, but it arose in part due to superior sales as the generation progressed. It was Combat Evolved that got their foot in the door.

The GBA sold 80 million in 7 years (FY/2002 - FY3/2008), that's a yearly average of 11.4 million.

The Gameboy needed over 9 years to reach 80 million, if the chart I found in an old thread is correct:

Yeah, a lot of my GBA games were SNES ports/remakes.

It was running the business at a loss that did the trick. Microsoft lost $4 billion on the Xbox over the course of four years. $4 billion is the equivalent of Nintendo hypothetically giving out 20 million $200 GC consoles for free.

The original Xbox was a failure without question and also easily a bigger failure than the GC, so get off this train of rewritten history that pretends that Microsoft somehow did a better job than Nintendo during that generation.

Halo wasn't anywhere near being a killer app, if the Xbox had a killer app, it wouldn't have sold 10+ times less than the PS2.

PS2 has sold over 250 million units?

And of course Halo 1 + 2 were killer apps which build a foundation for over 20 years Xbox platform.

Nintendo had a product that perfectly catered to people who wanted handheld videogames because it was cheap and had a really good battery life. Then Nintendo made the most genius console redesign of all time with the launch of the SP, making the GBA cool in addition to its other strengths.

Gamecube, by contrast, was everything the market of the early 2000s with its obsession with "dark and gritty" and "mature" hated. It was family-friendly with games like Mario and Wind Waker. It looked like a toy. Even its mature exclusives like Metroid Prime and Eternal Darkness could only reach a limited audience because they lacked the bombastic action of GTA and Halo. It wasn't until 2005 with Resident Evil 4 that the Cube finally got a big exclusive that actually catered to the gaming market of the time, and by then it was too late.

Even consoles that don't set the world on fire can have 1 or 2 system sellers, Halo is what propelled Xbox to 24 million instead of Dreamcast numbers. Those two games alone just weren't enough to rival the PS2.

There are lots of games on the GBA which I enjoy playing. On Gamecube, the only really exceptional game was the Fire Emblem one. This is just my personal preference, but I think the GBA has a much better game library.

Yeah I agree. Give the GameCube Halo 1 & 2 exclusive (with online play) may well take the GameCube from 22 million to well over 30 million. There would be a spin-off effect where that audience would in turn by other games and that grows everything. 

Like Halo 2 sold 4.1 million copies in North America in 2004 alone (so like six weeks worth of sales), that wasn't that far off from GTA: San Andreas (5.1 million) on the PS2's larger userbase. 

The XBox was even outselling the PS2 here and there for monthly periods by 2003/2004 in the US, MS just decided to pull the plug on the hardware because of a dumb hardware deals they had made with Nvidia that meant the chip was costing them huge losses and pivoted to the XBox 360 (moving to AMD). 

In a hypothetical timeline with a Delorean time machine, having the benefit of hindsight, I'd telling Nintendo and Microsoft of that time to do basically this:

- You're both going to get your ass kicked by PS2. In your case Microsoft, the XBox division is going to largely just be a money-losing pit for decades and you still won't ever beat Sony in the long run. The XBox hardware is also going to have a bunch of poor things about it and cause you to have to cut bait anyway. 

- So to Microsoft, you're better off just being a partner to Nintendo and throwing your money and influence to stake them in this high stakes poker game. In exchange I guess Nintendo could give MS the token nod of using Windows like the Dreamcast did. 

- To Nintendo: stop being fucking stupid with a lot of your weird hardware decisions. Take some notes from MS' XBox plans. No purple lunchbox design. Black and silver are the launch colors and the design is tweaked to look a lot cooler. RAM is bumped to 48MB main RAM, a modem is included for an online service. Full size discs, DVD playback is enabled by a seperate remote accessory. 

- That Wind Waker Zelda design ... not happening. Not at first. First you make Twilight Princess, then you can go make Wind Waker as the second console Zelda. Zelda is too important to have its sales potential crippled like that. 

Said joint platform (GameCube X lets say) should have titles like Halo 1/2, Zelda: Twilight Princess, Metroid Prime 1/2, Resident Evil 4, RE Remake, Super Mario Sunshine, Mario Kart: Double Dash, Eternal Darkness, Forza, Super Smash Bros Melee, Elder Scrolls III, Fable, Star Wars KOTOR, Star Wars: Rogue Squadron II/III, Zelda: Wind Waker (later), Animal Crossing, Ninja Gaiden Black, Dead or Alive 3, MGS2: Substinence port, GTA San Andreas port, Tales of Symphonia, Final Fantasy: Crystal Chronicles, MGS: Twin Snakes, etc. etc.