OG PS4, because it looks like an eraser ;)

my top 3:

PS2 (nothing beats that standing up with the blue stands) > org PS4 white (full matte) > PS3 slim

I also love the PS4 slim and Pro in white.

1. Playstation
2. Playstation 3 Slim
3. Playstation 3 Original
4. Playstation 4 Slim
5. Playstation 2
6. Playstation 4 Original

Subjectively, easily PS1.

You mean esthetics?

I uhh... actually think they're all pretty ugly.
I guess PS4 though, if I had to pick one, but it's still kind of like it's the turd that smells a little less bad.

EDIT: No wait, that grey PS4 anniversary console was actually decent looking, but it was more because of the color and the little button-logo's details that were on it.

PS4 is the most atheistically design. All the others are degrees of ugly imo.

Tie between Slim PS2 (So much goodness from such a small package and original PS4 (Cant get no sleeky and sexier)

But.....

If handhelds were/are allowed in this race then PSP Go takes the cake for me. It's sleek and small, real portable. It's compact when watching videos or listening to music, and then slides the controllers out when gaming. And its super sexy when docked to play on the big screen.

PS2 slim and fat PS3.

PS4 > PS2 S > PS3 > PS2 > PRO > PS3 S > PS1 S > PS3 SS > PS4 S > PS1

PS4 never truly felt like a launch console to me. It had too much performance for it's size, which was a shocker when they showed it. I remember thinking how did they manage to do it? I also remember thinking, who cares, look how small and sleek it looks! Well, until I started to hear the noise coming from the console, I then had my answer, and I did care now. lol.

I like how the PS4 is completely uniform, except for the light bar divider, which makes it seem a little less uniform than it really is. PRO seems too uniform to and a little bland me. PS4 S isn't uniform enough and just boring.

The PS2 was a stacked blocky design, but being able to stand it up, was wicked cool and made it look better for some reason. I really like how small the PS2 S was. It was just unbelievable that a device that small could do what it did at that time. The PS2 logo was really cool as well.

I like the PS3 big, bold, flashy design, with the chrome accents. The PS3 S was just a smaller more bland design. PS3 SS didn't have the smooth top and no indent where the disk would normally insert, even though it went in the top.

The PS1 was iconic with the central disk flip top. It didn't need great design to win anyone over at that time though. PS1 S was just a smaller version but looked better with the curved edges. 

Aesthetically I only like the PS1 and PSone, the rest of them I thought looked kind of boring.