Sonya
Mileena
Raiden
Kitana
Kung Lao
Sub Zero
Jade
Smoke
Liu Kang
Sindel

Honourable mentions
Kung Jin
Johnny Cage
Shang Tsung
D'Vorah

In no order:

Raiden
Liu Kang
Fujin
Kano
Shinnok
Quan Chi
Sub-Zero
Scorpion
Smoke
Goro

If I could only have eight characters on the roster, it'd be these. I don't tend to play female characters, and most of them are quite bland. Mileena and Tanya aren't too bad, but neither would make my top ten.

Scorpion
Sareena
Human Smoke
Kenshi
Sonya
Johnny Cage
Cassie Cage
Kotal Kahn
D'Vorah
Frost

Struggled a lot near the end.

1-Kenshi
2-Skarlet
3-Cyrax
4-Mileena
5-Erron Black
6-Kung Lao
7-Jade
8-Tremor
9-Reiko
10-Havik

1. Sonya
2. Kenshi
3. Kano
4. Jax
5. Tanya
6. Johnny Cage
7. Cyrax
8. Jacqui
9. Reptile
10. Li Mei

Of all time? Well I always rank in terms of which characters story interests me the most then gameplay second so I guess it would go something like....

10) Bo' Rai Cho
9) Tanya
8) Fujin
7) Li Mei
6) Cyrax
5) Raiden
4) Johnny Cage
3) Sub-Zero
2) Liu Kang
1) Kenshi

Honorable mentions: Smoke, Shang Tsung & Kotal Kahn.

1, Kobra
2, Li Mei
3, ashrah
4, kitana
5, sindel
6, ermac
7, sub-zeroes
8, fujin
9, Raiden (dark)
10,sweet tooth

NPO

Fujin
Shinnok
Bo' Rai Cho
Havik
Kabal
Johnny Cage
Sub-Zero
Raiden
Smoke
Nightwolf/Goro

to be honest though, there are really only a few MK characters I actually dislike. I like pretty much everyone for the most part, just some more than others. There are like 20 characters in my top 10 though, it changes all the time lol

Mine has changed dramatically. Edited my honorable mentions.
1.Tremor
2.Ermac
3.Fujin
4.Johnny Cage
5.Havik
6.Bo Rai Cho
7.Takeda
8.Cassie Cage
9.Kitana
10.Tanya
Honrable mentions they are 10 of them. Edited okay I lied they are 11 lol.
1.Erron Black
2.Raiden
3.Scorpion
4.Sub-Zero
5.Reptile
6.Mileena
7.Human Smoke
8.Cyrax
9.Sektor
10.Jax
11.Kung Jin

Noob Saibot (or more specifically, Bi-Han)
Sektor
Havik
Drahmin
Tremor
Baraka
Kano
Sheeva
Skarlet
Sindel

Honourable mentions to Goro, Kintaro, Motaro and Shao Kahn for being the coolest boss characters ever.

Nice, happy to see someone's representin' for her.

Hey,It is my second favorite character

1. Sub-Zero
2. Quan Chi
3. Drahmin
4. Kenshi
5. Goro
6. Sheeva
7. Johnny Cage
8. Reptile
9. Jax
10. Cyrax

Honorable mentions or just top 15-ers. Nightwolf, Jade, Noob Saibot, Baraka, Liu Kang

In order based on gameplay, story and design;

Noob
Smoke
Erron Black
Reiko
Scorpion
Kenshi
Goro
Kotal Kahn
Sub Zero
Ermac

In NPO

Shao Kahn
Havik
Shinnok
Kitana
Quan Chi
Bo Rai Cho
Scorpion
Sub-Zero
Tremor
Liu Kang

Blaze smaller super fast version
Johnny Cage
Mileena
Triborg is going to be Awesome
Skarlet
Taven will be Bad ass in MK 11

Still haven't played MKX (Thanks for cancelling the 360 version ) so I can't speak on the new characters:

Johnny Cage
Kung Lao
Tanya
Kenshi
Li Mei
Kano
Rain
Sonya
Mavado
Nightwolf

1. Frost
2. Moloch
3. Daegon
4. Kano
5. Khameleon
6. Jarek
7. Darrius
8. Erron Black

1. Kenshi
2. Cyrax
3. Quan Chi
4. Bo' Rai Cho
5. Takeda

Top 10 is a little murkier

1. Rain
2. Sheeva
3. Havik
4. Sindel
5. Ashrah
6. Cyrax
7. Kintaro
8. Tanya
9. Fujin
10. Nightwolf

Honorable mention: Ferra/Torr

You're right, I missed it. Sorry bro!

1. Liu Kang
2. Johnny Cage
3. Sonya
4. Kitana
5. Jax
6. Cyrax
7. Shang Tsung
8. Kung Lao
9. Shao Kahn
10. Kuai Liang

1. Jade
2. Kung Jin
3. Smoke
4. Sub Zero
5. Li Mei
6. Kenshi
7. Cassie
8. Mileena
9. Kitana
10. Kabal

This is about right for me, probably forgetting one or two... I also really like Kung Lao, Scorpion, Ermac, Noob and Tanya but not quite enough to make my top 10. Honourable mentions to Havik, Ashrah and Fujin who I really want to see return in future games.

1. Kung Lao
2. Subzero / Kuai Liang
3. Liu Kang
4. Kenshi
5. Scorpion
6. Kitana
7. Erron Black
8. Bo Rai Cho
9. Mileena
10. Shang Tsung

1. Mileena
2. Sindel
3. Rain
4. Sheeva
5. Tanya
6. Kitana (only MK2-MK3 era, I haven't liked her in any appearances since then... But I don't hate MKX Kitana. To me MKX is the first time since MK3 she hasn't been just... Blah)
7. Jade
8. Kenshi
9. Kung Jin
10. Sub-Zero