PS1

They managed to do something so unique that even Sony couldn't do it again

Game Cube is great and "kinda cute", but PS1 is the most iconic and classic.

PS1 for me.

PS1 by a mile for me lol. Maaaaaybe I would put the original Xbox at 2nd place.

PS2 and GameCube at the top. I'll also add Xbox and PS1.

I love the startup chimes of the GB, GBA, DS, and I suppose even the 3DS (least memorable).

GC is the best.

I remember that feeling of dread when the boot screen would take a little too long to transition to the game.

All I can think of when I see the Xbox startup is the early 2000's thing of words being spelt wrong, Xtreme Gamez and young teens with gelled hair and skateboards.

It reminds me too much of the cringe way games were marketed back then. I can imagine the people designing the xbox opening thinking how radical and explosive it was to appeal to the kids.

you are 100% right! That was really the demographic Xbox was targeting at the time. Whether the UI when you booted up the demo disc, the commercials including the dude who made the official video explaining how Xbox LIVE worked, it was all cringe by today's standards. But in those days, it was just fun lol. I was a pre-teen when Xbox released and I personally loved all the cliche's because the marketing wasn't taking itself too seriously. It was focused on stupid fun. 

I wouldn't want that type of marketing to come back though. It had its time. 

Exactly.
The longest 3 seconds of my life.

The Gamecube one made me smile, so I have to go with that one. The PS1 and PS2 are pretty cool though.