I just finished this and it was spectacular. I haven't played M2, Fu, or ZM, so it was all new to me and went into it blind, an experience I have not felt since Prime 3 nearly a decade ago. It has just enough linearity and small enough in scope to keep it from getting frustrating even when you get lost. Loved the music, loved the graphics, loved the enemies and environments, couldn't put it down (even when I was lost), enraged by the few boss fights, grateful for the ample save stations, in awe at some "story action" points, wishing it would never end.
8/10 for some boss fights, glitches, some powerup abilities that aren't fully explained, and a few sections that giftwrap powerups without putting up much of a challenge. If they had another few months it'd be a perfect 10.