I JUST finished Metroid Prime (haven't bought 2 yet but I'll be getting 3 day one) and while the first is a great game on it's own merits, I feel it's the only 1 of Nintendo's classic 3 franchises (Metroid, Zelda, and Mario) to not truly inherit the series' future. When it comes to Mario or Zelda, people expect the console-side games to be massive, innovative, and expansive 3D games. Their 3D transitions were overwhelmingly accepted. However with Metroid Prime, it feels like they lost that unique experience that was only available in the 2D Metroid games.
When playing the latter 2D Metroids (Super, Fusion, Zero), Samus controls so well that theirs almost something soothing and relaxing about playing the game. By the end of the game you can zip around so well that you feel totally connected to Samus and the world is at your command. It's one of the most intimate gaming experiences out there. However with Prime, it feels like they made the experience overly gritty/"hard." Just look at a run through Magmoor and see what it takes to get through: spider ball, grappling, wave beam, morph ball, space jump, etc. The environments themselves fit better into the worlds they're placed in, but it feels like the levels are done to do everything in their power to slow you down. Not to mention that putting it in first person adds things like blind spots, slower platforming, closed-in vision, etc. As much as I disagree with Igarashi's thoughts on Castlevania, his understanding (IN WORDS) of the different experience between 2D and 3D is perfectly exemplified with 2D Metroid/Prime.
Honestly to hate on Prime for not providing the same experience as a 2D iteration is to hate on all the things it does right. Taking in the environment in the 2D games is nearly a passive trait as you'll notice the little things as you pass by, but it won't necessarily make you stop in your tracks. With the 3D games, it's so much about the environment and looking around as oftentimes you'll need to do so to progress further. Not everything is in line of sight. The experience in general is top notch in Prime, with great music, artwork, and atmosphere. However I think a little part of Metroid was lost when the experience went from nearly an unconscious/passive one to one that is actively put upon the player.