[contains minor spoilers]
The main reason why I don't consider Metroid Prime 2: Echoes superior to the first Prime game is evident from its gimmick: you have to explore every area twice. I find that very few video games justify the use of this mechanic, as it tends to come across more as lackluster padding than a necessary expansion to "original" world (the Silent Hill series being the notable exception). That's not to say any game that uses this concept is automatically bad, but exploring two identical environments makes a playthrough feel significantly longer. Even though Metroid Prime 2 features more interesting abilities, puzzles, and settings than the first, it does not escape the detriment of the "dual worlds", especially considering that it's placed into a franchise teeming with backtracking segments as-is.
It's difficult deciding whether or not to air my complaints or compliments first, since a lot of them are inextricably tied together. For instance: the ammo system. Attaching ammunition to opposite beam types strengthens the combat, since you're forced to decide whether you want to endure a long battle at the potential cost of your health, or fight a short battle that quickly depletes your ammunition. Missiles had always served this purpose, but every enemy was weak to them in equal measure; the Dark and Light beams are primarily world specific, forcing you to weight your options before jumping into a trans-dimensional warp-gate. Add in the missile combos for each weapon and you're suddenly looking at a Metroid that's surprisingly resource intensive, and therefore a lot more engaging on the survival front.
Buuuut ammo in Metroid Prime 2 is scarce and unreliable. Beam recharge centers are only available in the dark worlds, and there's a number of bulky enemies that drain your munitions should you choose to fight them. This leads to my second point—foes are too durable. This was a complaint from the first game (and similarly, I'm judging it based off the game's hard mode), but the problem is greatly exasperated here. The Ing are shockingly resilient to the Light Beam and since the missile combos cost so much ammo (it really should've been about 20 missiles & 20 ammo), you're frankly better off skipping a majority of the encounters. The Dark Pirate Commandos are the worst offenders, as without the Dark Beam (which they shouldn't be weak to?), fights against them take so long that the brigands just up and leave after a certain amount of time elapses—but the doors are locked until they decide to do so.
This is a shame since the enemies you'll encounter in Echoes are more diverse and fun than in the original Prime. A number of familiar critters return but there's also plenty of new fauna to interact with, the most interesting of which is saved for the final area of the game. Bosses are also more engaging, utilizing your own power-ups against you in creative ways (the Spider Ball Guardian being my favorite sub-boss). But outside of these titanic tussles, there's not much of a point to challenging the Ing forces. Had larger foes dropped more bountiful caches of ammo & health, maybe I'd be singing a different tune. Luckily, puzzles are much more challenging and extensive in Echoes, so I have no qualms in that department. I also appreciate that the game isn't too taxing to 100% without a guide.
If my entry thus far seems fairly negative, I don't intend it to be; following up on Metroid Prime was going to be a difficult task for Retro Studios, no matter how hard they tried. In a way, I'm kind of glad they aimed to go "bigger and better", as the ambition on display here is commendable. Power-ups like the Echo Visor and Screw Attack are excellent additions—the timing on the shift from first person to third for the Screw Attack is remarkably fluid. Each major area loops around itself quite nicely, allowing the player multiple paths to reach their destination during backtracking. Each setting is simultaneously gorgeous and lonely; Sanctuary Fortress in particular is a breathtaking sight to behold, really drilling home how utterly amazing the art team is. Lastly, the Ing have a menacing and grotesque design, perfectly befitting of their monstrous nature. The aesthetics of the game alone make it worth playing.
Lore-wise, I'm satisfied with what's presented here, though nothing in particular really blew me away. I think part of the problem is that there isn't much of a distinction between entries of the Light and Dark versions of each creature—it would've been interesting to read about how the Ing repurpose certain animals and technology for more than just warfare. I mean, their emphasis on battle accurately conveys the priorities of the Ing, but their civilization has a hierarchical structure that barely gets touched upon, and I feel like more entries could've been written around that. Perhaps I'm a little disappointed because the Ing aren't nearly as fascinating and flawed as the space pirates are... at least uncovering the various ways the Luminoth honorably stood against their hordes was intriguing (as well as tragic). Oh, and I quite like the area names given on the map of the Dark World—what's not to love about "Bitter Well", "Profane Path", or "Doomed Entry"?
Finally, I need to harp on the return of my lest favorite Prime aspect: mandatory endgame item collection. Echoes is ~50% longer than Metroid Prime due to repeated visits you'll undergo to the Dark World, an aspect that gets amplified when you're forced to find the nine Sky Temple keys. You spend enough time in each locale that the requirement to go through them all again just feels like a waste of time, especially considering you've essentially traveled through them twice as is. It doesn't help that the structure of the overworld requires repeated visits to the Great Temple (until the end of the game), and that returning power to each of the energy controllers is dull and uneventful. The interlocking layout cuts down on the tedium, but just barely.
Metroid Prime 2: Echoes is a sturdy sequel that expands on the Prime name in interesting ways. It's unfortunate that the "interesting ways" make the game a mixed bag; none of Echoes' concepts are bad, it's just that the execution leaves a lot to be desired. Nevertheless, I greatly enjoyed my replay of Echoes; sadly, there was just no way to turn off my inner-critic while I played it. If you enjoyed Metroid Prime I see no reason why you won't value and cherish Echoes as well, but prepare to feel fatigued once the journey is over.
Images obtained from: metroid.retropixels.net, Giantbomb.com