With a slimmer PS5 out soon (and rumors of a slimmer, all-digital Xbox Series X), what are some of the best and worst platform revisions out there? 

What doesn't count: "Pro" versions (I feel they deserve their own thread to rank), minor adjustments that aren't named (serial ports changing on the PS1, PS5 getting slightly smaller without changing the plates, when Switch got a better battery), and hard drive amounts that change over time (Xbox 360 Arcade, etc).

Just about anything else is fair game. You can mention the slimmer PS5 as one of the best or worst, but that's one to take with some grain of salt since it hasn't released yet. 

Ps1 to ps1 mini was the best.

PS3 Slim to PS3 Super Slim is probably one of the worst. The Super Slim just looked and felt cheap.

I like Nintendo 2DS XL

Removed a close to useless gimmick, has a bigger screen and had a great portability

Best.

PSOne

Xbox 360 S (not the E)

SEGA Genesis Model 2

PSP 2000/3000

Game Boy Pocket/Color

PS3 Slim and Super Slim

PS2 Slim

SEGA WonderMega

TurboDuo

SEGA Nomad

Neo Geo CDZ

Neo Geo Pocket Color

Xbox One X

DS Lite

Wonderswan Color

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Worst.

SEGA Genesis Model 3

Wii Mini

SEGA Master System 2

Xbox 360 E

PSVita 2000

PSP Go

PSP Street

Xbox One SAD

Xbox Series S

Game Boy Advance Micro

TurboGrafx16 from the PC Engine (they made it larger and ugly for no reason)

Every 3D0

Every CDi

Jaguar was ugly but Jag CD made it look like a toilet.

2DS

PSP Go lol

GBA SP and DS Lite were my favourites.

Can’t say I can think of a worst one. Just something that wouldn’t be in the market for me… something like 2DS, probably - as the idea of it felt like Nintendo giving into the moronic anti-3D paranoia. That said, the 2DS would be perfect for kids with paranoid parents who bought the whole “3D causes seizures and eye damage” narrative and didn’t want to buy their kids a 3DS.

Best

• PSOne: Smaller and even had an SKU with a cool LCD screen attachment for car rides and other occasions.
• GBA SP: Clamshell design, lighting, rechargeable battery
• DS Lite: Slimmer and brighter screens
• PS3 Slim: A much slimmer console at a great price. 
• PSP 2000: Slimmer, brighter screen, and a much-needed doubling of RAM (from 32 MB to 64 MB). 
• Xbox 360 S: Slimmer and built-in Wi-Fi
• Xbox One S: Smaller and includes a 4K Blu-ray drive. 
• PS4 Slim: Very simple but it's cheaper, better-looking, quieter, and slimmer. 

Worst

• Wii Mini: Already got an issue with the Wii Family Edition for removing GameCube controllers, GameCube memory cards, and a stand? Say no more, there's something worse. The Wii Mini takes the Family Edition and removes the internet and 480p/component video output. The loss of features is not worth what you would have saved back in the day.
• PSP Go: This was too ahead of its time in Q4 2009 as far as digital distribution goes. While it did include 16 GB of storage, most core gamers would have to pay up to get more memory sticks. 
• PSP Street: No Wi-Fi, mono speaker, no microphone, etc.
• 2DS: A bizarre dual-screen slab. That's the bigger problem than losing 3D support. The button layout is also quite weird.
• Xbox One S All-Digital: A lazy SKU right here. The optical drive was ripped out and the slit closed, but there is now a void in the shell if you pop it open. Not to mention it retailed for $249.99 while still only having 1 TB of storage. it did come with Forza Horizon 3, Minecraft, and Sea of Thieves. But if Microsoft was going to charge $250 anyway, they might as well let you pick 1-3 games with a voucher. 

Any I didn't mention probably just didn't come to mind or are in a grey area. 

The slimmer PS5 might belong in the worst category because:

The digital is hiked to $449.99. Revisions should be the same price or cheaper, not more expensive. While the console SKUs include a tiny vertical stand, they don't include a vertical stand. You have to pay $29.99 for that. While I'm a function over form person, I'm still interested in form as well. The slimmer PS5s look really similar to the older PS5, but uglier. There's an extra divide in the plates now. I was really hoping for a more angular look that PlayStation is more known for. Maybe we'll get a PS5 Super Slim one day that looks more like a PS4. 

I have a real soft spot for the SNES Junior; it's just so gosh darn cute

PSOne is up there as well, it was very small and compact, and fun to look at

Worst? The PS3 slim and super slim sucked, they looked cheap and nasty compared to the fat model and cut back on features. PS5 slim hiking the price deserves a dishonourable mention as well.

I think PSP Go was a good revision because it made it pocket sized. Thought going digital was a slick feature at the time. 

I didn’t like the colored N64s. They didn’t look sleek to me.