Sheeva's seems to have a lot of range on it. Moving this to the gameplay forum.

Worst: Kratos
Best: ?

I'm not sure about the worst, but, I'm pretty sure I've read in many places that Sonya's got the best uppercut do to its great speed.

High level players would know better.

Cage has a pretty fast uppercut.

These are officially the fastest uppercuts. Being fastest does obviously not equal best, but it is something we can get a definite answer on. Something like range would also play a huge part.

Kung Lao : 7 frame
Johnny Cage: 7 frame
Nightwolf: 7 frame
Sonya: 7 frame
Stryker: 7 frame
Liu Kang: 9 frame

Baraka and Sektor also have good ones with Baraka's having most range (I think) so maybe there is at least one thing the poor guy is good at in this game.

From what I've heard Mileena has a pretty poor uppercut, though I don't really employ uppercut as a big part of my "strategy", so I wouldn't know the difference.

The thing is that most characters have better options than an uppercut. Would mostly be used as an anti-air but it's almost never the best option. Having said that there is just something very "retro-MK" and satisfying about ducking someone's uppercut and nailing them with your own.

Also I can concur that Shang Tsung has the worst one of the bunch.

You should start a thread with people giving there opinions on who has the best and worst sweep. Barraka for sure has the slowest and I know Kitanas is pretty fast.

According to official stats:

Fast Uppercuts:
Noob Saibot, Sonya Blade, Kratos, Stryker, Quan Chi, Sektor, Jax, Nightwolf, Kung Lao, Johnny Cage, Liu Kang

Average Uppercuts:
Scorpion, Sub-Zero, Kabal, Cyrax, Sheeva, Kitana, Shang Tsung, Kano, Reptile, Ermac, Cyber Sub-Zero

Slow Uppercuts:
Baraka, Sindel, Mileena, Smoke, Jade, Raiden

I've definitely noticed Sonya's as pretty damn quick, and Jade's sucks ass.

According to the wonderful Kollector's edition guide:

Fastest - Sonya, Noob, Kratos
Fast - Sektor, Jax, Cage, Liu Kang, Nightwolf, Kung Lao, Stryker, Quan Chi
Average - Scorpion, Sub-Zero, Shang Tsung, Kano, Reptile, Ermac, Kabal, Cyrax, Sheeva, Kitana, Cyber Sub-Zero
Slow - Sindel, Baraka
Slowest - Mileena, Raiden, Jade, Smoke

Edit: According to TYM, Kenshi's uppercut clocks in at around 14 frames....Ouch!

Maybe OP could just modify his Subject? Then we discuss both here.

All I know off the bat is that Smoke has the fastest sweep (makes up for his slow-ass uppercut i guess.)

Sindel's is pretty slow but it seems to have quite a bit of range. Sonya's is very very fast with decent range and works as an excellent follow-up.Definitely my favourite. Mileena's is pitiful but it seems to have gotten slighter better than when the game first came out.

Best - Baraka (Has great range)
Worst - Kratos (Quite a lot of recovery time on it)

Once again, I hear Mileena's is quite bad... Though her wonderful "Getaway Sticks" solves that problem.

So, there's really no definite answer for now?

Does this also depend on the opponent?

The opponent's hitbox can make it easier to hit an uppercut from different heights and distances.

As for the best uppercut, we would need the frame data for all of the characters' uppercuts (startup and recovery frames) to make that determination. We can all tell what uppercuts are quick, and which ones are slow, but to definitively determine the best, we need data.

I may start this as a little project.

The best uppercut? Of course Sonya!
She beats the strongest and fastest and pretty uppercuts! As a character, she is average, but she very like uppercuts, and beats them very often.

The worst... I think Kratos or Shang Tsung. They dont prefer to do this.

In MKX, idk about the best but even tho I don't play him, I feel like Takeda's is the worst lol its recovery is painful.

Not a big fan of Kung Lao's. Shinnok's is decently fast, and so is D'Vorah's, Kung Jin's, and Liu Kang's.

Best uppercut hands down is Cryomancer Sub-Zero. That reach is HUGE since the sword creates such a wide arc.