If you want to learn about the story of MK, start by watching all the arcade endings for all the characters in each game. There are videos of character endings on youtube. Watch every character ending from every MK game, MK1-MKX. Do this as a way of "playing" each game without having to go through extraordinary means of actually buying a SNES or Gamecube to play the old Mortal Kombat games.

You'll see that some endings contradict others but you'll find out the true and canon version once you watch the endings of the next game. For example, Scorpions and Sub Zero's endings in MK4 tell a different version of events, but the true one comes out in MKDA. Don't forget to watch streams of Konquest mode from MKDA, Mortal Kombat Deception, and Armageddon, as a lot of story is told in those Single-play campaigns. Mortal Kombat Mythologies is also important, but you can just watch a stream or read a wiki synopsis with that one because the game isn't very good or fun. It's still charming in a way, and there are cinematics that introduce important characters and their stories. Also, Mortal Kombat Mythologies is a prequel to Mortal Kombat 1's story, and the story from that game still hold true to this day.

It's true that Mortal Kombat 2011 is a reboot, but the way it is done is remarkable. There is still one story being told. You don't have to indulge in the Character endings at this point, because there is a coherent and official account of the story presented in the Story Mode. Same goes for MKX.

You can visit the Mortal Kombat Wiki to fill in any gaps you're experiencing. Going straight to the wiki might spoil the experience of watching the endings. http://mortalkombat.wikia.com/wiki/Mortal_Kombat_(1992_video_game)

By the time you've enjoyed the endings, Konquest and Story modes, and pay the occasional visit to the wiki, then you can consider yourself a true Mortal Kombat Scholar!