My favorite to least favorite.

UMK3
MKII
MKD
MK9
MKvsDC
MK4
MKDA
MKA
MK:SM
MK1

Oh allright.

MK;A
MKM;SZ
MK;SF
MK4
MKvDCU
MK;DA
MK3/UMK3/UMK(DS)
MKT
MK;SM
MK1
MK2
MK2011
MK;D

Worst: MK4
Best: tie between UMK3 and MK9

Gotta do all the games.

Haven't played them all:
Least liked to Most Liked:
Gold (Buggy piece of shite)
MK4
MKD
MK1
MK2
MKArmageddon
MKDA
UMK3
MKTrilogy
MK VS DC
MK 2011
MK Shaolin Monks

How on God's green Earth is Special Forces not number one, let alone have two games behind it?

Best to worst:

MK9, MK1, MK2, MK:DA, MK:D, UMK3/MK3, MK:A, MK: Trilogy, MK4, MKM: Sub-Zero, MK Spec. Forces, MK11 (yeah, vietnamese hacked cartridge, it had three Liu Kangs and of them was Bruc Lee. Bruc Lee.)

Favorite to least favorite:
MK9, Shaolin Monks, Armageddon, Deception, Deadly Alliance, Trilogy, 3, 2, 1, 4, Mythologies.
those are the only ones that I have played.

Least favorite to favorite (as the OP asked us to do).

MK Advance (GBA)
MK Special Forces
Mortal Kombat 3
Mortal Kombat vs DC
MK Tournament Edition (GBA)
MK Deadly Alliance (GBA)
MK Armageddon
MK Mythologies: Sub-Zero
MK Trilogy*
Ultimate MK3 / UMK* - this is where my "real favorites" start -
Mortal Kombat 4 / Gold
Mortal Kombat 1
MK Deadly Alliance
MK Deception / Unchained
MK Shaolin Monks
Mortal Kombat (2011)
Mortal Kombat II

*UMK3 & MKT get higher scores than MK3 because they have my favorite characters.

Nothing can ever touch MKII. Never. Period. Done.

Never played UMK3 for iPhone so I don't know where that would fit.

Since i havent played every version of every game ill keep it by game itself:

Least fave to fave:
MK VS DC
MKA
MKSF
MKD
MKDA
MKSM
MKMSZ
MK4
MK3
MK2
MKT
MK
MK2011

Least to Fave

11. Mortal Kombat vs DC Universe
10. Mortal Kombat
9. Mortal Kombat 3
8. Mortal Kombat Deadly Alliance
7. Mortal Kombat Armageddon
6. Mortal Kombat II
5. Ultimate Mortal Kombat 3
4. Mortal Kombat (2011)
3. Mortal Kombat Tournament Edition
2. Mortal Kombat Deception
1. Mortal Kombat 4


Honorable Mentions
Mortal Kombat Advance
Mortal Kombat Unchained

Dishonorable Mentions
Mortal Kombat Special Forces
Mortal Kombat Shoalin Monks

mortal kombat gold
mortal kombat 4
mortal kombat 1
mortal kombat 3
mortal kombat 2
mortal kombat mythologies: sub-zero
mortal kombat: armageddon
mortal kombat shaolin monks
mortal kombat ultimate 3
mortal kombat deadly alliance
mortal kombat deception
mortal kombat 2011
mortal kombat trilogy

Least favourite to favourite:

Mortal Kombat
Mortal Kombat 3
Mortal Kombat Deadly Alliance
Mortal Kombat Deception
Ultimate Mortal Kombat 3 / Trilogy
Mortal Kombat Armageddon
Mortal Kombat 2
Mortal Kombat 4
Mortal Kombat Shaolin Monks
Mortal Kombat (2011)