Metroid Prime had the most beautifully constructed game world ever.  It
coupled that with great 'converted from 2D' gameplay that was fresh and
original.  It covered a huge area consisting of several levels, all
interconnected and freely explorable, with very little repetition of
geometry.  Every tree, rock, and wall was unique.  And even though the game
is free roaming and detailed, the game avoided losing the player's attention
with load times by its clever use of streaming and cutscenes.

Metroid Prime 2 continues everything Prime 1 introduced, from the
unsurpassed immersiveness of the "in the helmet" view (with moisture beads,
face reflections, etc) to the meticulous detail in every bit of its
indoors-and-outdoors world, to the perfectly-translated-from-2D jumping and
morph ball puzzles and combat system.

It's a masterpiece, just like the last game, but set in an even larger and
more detailed world (though not as varied in theme), with more abilities and
a longer play through time, and an added multiplayer mode.
But not everything is improved.

The Light and Dark world theme is sometimes clever as you wonder how to get
to the same place in one world as you have been in the other, but many of
the puzzles are "gimme" puzzles, because the game insultingly spells out the
solution for you as if you're not only too dumb to understand how to solve
it, but also too dumb to know when you've solved it and must be told.  Other
puzzles are much more subtle and clever, notably some of the morph ball
sequences.

Also, the Light and Dark Beams are generic and not as fun or interesting as
the Wave and Ice Beams they replaced.  The ammo system is a dose of reality,
but mis-placed in a game where enemies drop "powerups" and doors are
weapon-specific (how does anyone but Samus get through them?).
That bit of reality would have been more welcome in other aspects of the
game.  For example, the game introduces some and re-uses other types of door
locks.  Most of them are door "covers" and must be broken or keyed open only
once, leaving the "normal" door behind that can be activated by any weapon.
That should be the case with ALL doors, rather than leaving 3 other types
that are weapon-specific, which is annoying and unnecessary.  The game's
system of using acquired abilities to access new areas is time-honored but
never gets old, but a "Light Beam Lock" would accomplish that as well as a
"Light Beam Door" that must be shot with the Light Beam every time rather
than just once.   And the re-appearing enemies, though they do change over
the course of the game in some areas, could benefit from a little
randomization, even controlled randomization among a couple of enemies
and/or placement (especially the War Wasp nests).

On the other hand, weapon-specific enemies are mostly gone, replaced by
enemies defeatable with any weapon but weaker against a specific one.
That's very welcome--more believable and open-ended while also being more
challenging, since you won't immediately know which weapon is THE weapon you
must use.

The story is nothing more than it has to be to justify the gameplay.  In
other words, it's bad.  Dark Samus is a dumb idea, and not only that, but
she is neither explained for those who might not have seen the last game's
hidden ending, nor is she further revealed for those who did see it and
wonder what she is, why she's there, etc.  And her use as an antagonist
draws the story away from the completely uncharacterized (other than "evil")
Ing and poorly characterized (in comparison with the Chozo) Luminoth, and
also away from the Space Pirates, whose logs drove the story in Metroid
Prime 1, but who are only incidental enemies here, and who are completely
forgotten long before the end of the game.

The story is told mostly the same way as before--through brief cutscenes and
from scanning the environment.  It works fine, but can become monotonous.
There is one time in the game, though, when scanning a log triggers a
cutscene.  I felt that worked well, and I would have loved to see other key
scans played out in video.  And the logs of the soldiers and key Luminoth
could have been audio logs, which would have made much more sense than
reading a trooper's log that says "Agh! What's that? No! Don't--".  That one
cutscene--the only one not set in the present--was a hint of lost potential.

The enemies are numerous and varied, much more so than in most games.
They're well drawn and well animated.  The re-use or re-naming of some feels
cheap, but the complete lineup of characters is huge and diverse, and very
satisfying.

The boss battles are a highlight, of course, and they're mostly very well
done.  A couple have stages that are longer than they should be, but on the
whole the bosses are challenging but not too frustrating, and my only real
complaint is that some of them have multiple stages or even body parts that
must be scanned to get 100% on your Logbook.  That is a cheap trick, and to
reach the end of the game and find that you didn't scan a "stunned Boss
head" when there are already FOUR entries for that boss seems completely
unfair.   But when you're not paranoid that you might miss a scan, the boss
fights are a blast.

The game is paced over a kind of exponential curve, with the difficulty
increasing as your skills and abilities do, and it's a very back-loaded game
in the powerup department--just when you think you must be closing in on the
end, you gain several more abilities and therefore new areas to explore.
It's a lengthy game, even more so if you turn off the Hint System (on by
default).  With that off, it took me 35 hours to beat the game with 100%.

The multiplayer mode is mildly entertaining at best, forgettable at worst.
It has potential that is wasted by there being no options at all (the option
to turn on or off each powerup would have been a huge improvement, since
some of them are randomly picked, impossible to turn off, and useless--a
terrible combination).  I'm predicting this mode will be ignored by most,
and that is what I'm doing as well.

In the end, I rate this game as dead even with the first, and I consider
that possibly the best game of this console generation--certainly it is in
the areas of art direction, immersiveness and level design.  The good and
bad in Metroid Prime 2's additions nets out as a slight improvement, I feel,
but in its favor Prime 1 had the feeling of newness that a first-time 3D
installment of a franchise brings with it, and the originality of the
immersive visor interface and 3D morph ball puzzles.  So that means I place
this game at the top of my list along with the best games ever made,
including others of the Metroid series.