Mortal Kombat 2, my cousin had it on his Genesis, I thought it was the most fun game I ever played.....

But then my uncle got MK1 on his super nintendo and since then I loved it

I know it may sound dumb, but it has to be MK4 (Stop laughing, is for real!)
The first one I saw was the good ol' MK2, when my cousin bought it. I can still remember a few battles we had in his home, and how hard I try to made everyone's fatality. At the beggining I couldn't do a single one, but after some practice I was able to pull most easily (except Jax's arm rip, it seems I always miss the distance).
When MK3 was out, I had my own SNES. unfortunately, the MK3 I bought was giltchy as hell (The Animalities were all messed up and Nightwolf's Thundershock fatality hooked my game). Then I bought UMK3, but it wasn't the same without my cousin, so it eventualy fade back.
Then one day I went to the Arcades and saw some guy winning MK4 with Sub-Zero. That ending was gold that time! Only seeing Quan Chi's face roll close the screen was amazing! I went regularly to play it (with Dead or Alive as second choice) and was half the reason I bought a PSX (the other was that my lil' bro wanted a Dragon Ball game that saw in TV). Since then I had bought MKM, MKT, MKSF, MKDA, MKD, MKSM and MK2 (for PSX). Heck, even that game made me return to play my "dust collector" UMK3 for SNES and was able to beat it with all the characters.
So to resume all the story began with MK2, but finally was stablished as one of my favourite after MK4.