From a story perspective this is probably the best Mortal Kombat game, taking the classic foundational first three games and reinventing them into a coherent single plot. It's also a really innovative form of game that became the foundation for everything Netherealm has done since, and much of what other fighting games have emulated. Oh, and it's good fun to play.
Despite that it's no longer legally available to acquire, presumably because it was bundled into a Komplete edition with guest characters and the publisher probably lost the rights and decided it was too much trouble to remove those characters, rather than just remove it altogether from stores.
Give us back MK9!