Some startups I like:

Gamecube is my personal favorite. I do really like the PS1 as well. The wind instrument at the end feels very cultish or spiritual in a sense--like it's a call to worship at the altar of Playstation.

Original Xbox.

It's so badass, like a nuclear reactor firing up, and really captures the feeling of power and "hardcore" vibe the brand had back then.

PS1 and GameCube (I held the A button a moment before the end of the animation for a quirky added effect!)

Oooh, good question. Top three for me:

1. PS1 - Sounds so technological. Like a declaration that the little console unit is a piece of tech with circuits and processing units. Nice and meaty in duration too.
2. XBox - You're dealing with power! Inside the console is an energy source capable of great strength and fury and only XBox can contain it! Handle with caution!
3. PS2 - Similar to the PS1 start up but not as lengthy or meaty. I love the artificiality of the start up chimes, fitting for what is a box of computer machinery.

Sega Dreamcast

Gamecube and PS1.

And the original Game Boy. One of the single most recognizable sounds in gaming.

It's between Dreamcast and PS1 for me.

I never had an Xbox, but whoa, that's a cool one!

I'm digging the xbox series intro. It gives me the dolby intro vibes, especially when the volume is up loud.