DISCLAIMER: Played with an English patch that changes some of the dialogues. Bosses names and certain attacks also were maintained as they were on the Japanese version.
This is the best SNES MMX game, in my opinion.
It improves on a lot of the features that the first game had and makes the game even faster paced. The story itself is simple enough to understand and follows the events of the first game nicely. Counter-Hunters are trying to maintain Sigma's Revolution going, as X defeats the Mavericks one after the other. The game does imply that Serges might be a revived Doctor Wily, but it doesn't go much further than that.
Gameplay-wise, it's so much faster than X1 and the level design itself is much more interesting, almost forcing the player to use all available weapons if he wants to get all the extra items.
While soundtrack-wise it doesn't sound as complex as the first one, the compositions feel much more interesting and most of them returned in one way or another to the franchise at some point.
While "stage changes" are not so much of a thing anymore, I like that they maintained the whole "You can change how the boss looks depending on what you use against it" that started on X1.
Overall, this is my favorite SNES X game.