Wrapped up Metroid Prime 4 last night and really enjoyed it. I could 100% have done without the whole Viola and open world part, and I honestly think they tacked that whole part onto the game because the game was going to be like 8 hours long without it, and maybe they did not have time to design and add more actual dungeons or something. I dunno it just felt like everything about it was half assed, from the way it drove, to the combat on it, to the way the crystals broke when you ran into them, to how bare it was out there although it had a few things to do.
That said, they sure as shit know how to make you want to run into those god damn green crystals. Every time I saw one I had to go smash it and the sound it makes when you do is so satisfying as well lol. I didn't really get bored driving around from place to place because you would find shit to drive through, and I actually never had to "farm" the crystals either. By the time I was ready to go to the final part of the game I had more than enough of them from just going back/forth to places and exploring the entire map.
The NPCs don't play nearly as large of a role as they make it seem from the complaints about it. I also think some of the weapons are kinda "meh" especially the power ups you get for them. I really only used one of the maxed out weapons for the most part, and then the other 2 I really used one of the like 90% of the time and the other one like 5% of the time. The missles were used a bit until I got the other abilities though.
I thought the final boss was WWWAAAYYY harder than any other boss in the game. I didn't die once at any other boss and then the final boss kicked my ass for a bit. But then after I actually figured out how to fight the final boss and counter each part, it was one of the easiest bosses lol. When I finally beat him I had like 75% health left.
Overall it was a great game and I highly recommend it if you like previous Metroid Prime games. Yes it's not 100% like the others (never played 3 actually) but it definitely feels like Metroid Prime that you know most of the time.