All. Even SF.

All of them on multiple systems including Arcade

MK 1:Snes, Genesis
Mk 2: Snes, Genesis, Arcade Cabinet(Love It almost as much as my dog, ....It cost me 2000$ I was stupid enough to buy it, wait , nothing is stupid when it has to do with mk... awsome
MK 3: SNES Genesis
MK 4: PS1
MKDA: X-BOX
MK D- X box
MKA- Ps2 and XBOX
MK SM: X box.

i had MKT and MK4 but they were stolen I currently own

MKDA
MKD
MKA
MKSM
MKMSZ
MKSF

I have the special editions that have arcade versions of MK1-UMK3

Ok...

1. MK (GameGear)
2. MKII (GameGear)
3. MK (SNES)
4. MKII (SNES)
5. MK3 (SNES)
6. MK3 (PSX)
7. UMK3 (SNES)
8. MKT (PSX)
9. MKT (N64)
10. MK4 (PSX)
11. MK4 (N64)
12. Mortal Kombat Advance (GBA) (Worst fucking game ever)
13. MKDA (PS2)
14. MKD (PS2)
15. MKD (NGC)
16. MKA (PS2)
17. MKU (PSP)
18. MKSM (PS2)
19. MKvsDC (360)

19 games so far. I'll be getting MK2011(360) when it comes out to give me an even 20.
If ROMs count, I also have MK (MAME), MKII (MAME), MK3 (MAME), UMK3 (MAME), MK4 (MAME), and MKTE (GBA) That brings me up to 26. If the ones on Midway Arcade Treasures count, I'm up to 28.
This is why I laugh derisively at people who say I have no business posting here.

ALL Main mk games except for mk4

Console:
Mortal Kombat II (From MKSM)
Ultimate Mortal Kombat 3 (From MKA)
Mortal Kombat: Deadly Alliance
Mortal Kombat: Deception
Mortal Kombat: Shaolin Monks
Mortal Kombat: Armageddon (Premium Edition)

PC:
Mortal Kombat
Mortal Kombat II
Mortal Kombat 3
Mortal Kombat Trilogy

NOTE:I don't technically own the PC games, but they are all abandonware, so I can dl them any time... legally... same thing in my book...

MK Mythologies Sub Zero (PS1)
MK1 (Genesis)
MK2 (SNES)
UMK3 (SNES)
MK4 (PS1)
MK Deadly Alliance (Xbox)
MK Deception (Xbox)
MK Armageddon (Xbox)

so 8 games in total, i use to have Shoalin Monks & vsDC but i sold them a while back.