I've not ever thought much about this. I'll have to kick it around some. Off the top of my head, I'm thinking it might be Sega Saturn.

Though I don't think I'd vote for any XBox in the OP's poll, I do think its worth noting that I've always really liked the XB green color. When I fire up an Xbox and see that logo and the bright green color, my gaming senses get rolling, and my game mode turns on automatically.

all 3 of them are iconic from my days of smash, the Samurai one being that time you got 3 mates around to all hold your Z buttons before a good session of smash is going down.

The PS2's is my fave

The OG Xbox logo and startup made the system seem more powerful than the rivals in my mind, it seemed more heavy duty (and not just because the console doubled as a doorstop) but the deep rumbling green heart inside the Xbox logo to be greeted by that menu which sounded like the ocean along with a HDD full of named ripped CD tracks on it. Felt like a cool mix between consoles and a PC which it pretty much was at the time.

Are startups just practically dead now? Lol

PS2. It's got the best balance overall as far as I'm concerned. Not too flashy but not too basic and boring. The sounds though I find unbelievably unique and catchy for whatever reason. The OG 360 startup I would say is my second fav, with GCN being third.

PS1 or the second Xbox 360 start up.

The Xbox One X start up sequence is also really good.

https://www.youtube.com/watch?v=HrPRtYvCvZI

My first PC, a 286. Still remember all the sounds it did (from checking the memory, the CPU, the GPU, the drives and the extension cards) and the sequence they played. Wish I had it recorded at the time, because it was very iconic.

Another blast from the past: My most hated boot sequence is from our old 56k modem. God, were those things annoyingly noisy.

Atari 2600.

There was none. Flick the switch > game. Done.