Between loving this and Cyber Shadow, I really feel like I'm overdue to actually play NES Ninja Gaiden. As for the game itself, the Messanger more or less starts as a traditional stage based platformer then about a 3rd of the way through it turns into a metriodvania. Admittedly, I'm more of a stage based platformer fan since I generally dislike having to figure out where I need to go in games. I think the switching between 8 bit and 16 bit aesthetics makes the experience a little more engaging though. Plus, it's during this portion of the game, you really get a chance to really get a feel for how much expression and quickness the game mechanics allow.
I will say, across my many playthroughs, I've never fully come to appreciate it's story all that much. At the start, it's just a bit too tongue in check to get all that invested. The plot picks up in the 2nd half but it never really gets out of the silly billy lol video games are weird attitude to really feel the build up of the parts that I feel work. This isn't to say I think none of the humor works but I kinda wish it took itself seriously more often then it did. I also wish it spread it's actual lore out more instead of dumping most of it at the very end. Anyways, if you're like me and find yourself caring more about gameplay than plot, this won't be the biggest issue. I'm just not going to act like, this isn't something holding it back a bit.