POKEMON RUBY/SAPPHIRE/EMERALD / Nintendo / Gameboy Advance
                                    I'm Prof. The Dude
Nintendo played this sequel about as conservative as possible, down to retaining the old-school four-direction-only tile movement and no animations in battle. There was also the inevitable "upgraded release" of Emerald a few months later, which added the battle animations and a bunch of little optional extras to entice you into double/triple-dipping for the same game.
                   AND ALSO REALLY DANGEROUS

We've moved to the new Hoenn region for this outing, however, so that at least means a roster of almost entirely new Pokemon. Same basic formula of gradually challenging the Gyms for their Badges, learning the HMs to bypass conveniently placed obstacles, and getting sidetracked into a quest involving some evil Team messing with a slumbering legendary Pokemon and unwittingly threatening the world with destruction before moving on to the Elite Four and finally seeing the credits roll when you become Champion.

We're also no longer following Red, or Ash's two-decade quest to be a perpetual loser ... instead this time you get a new protagonist and the first choice of unique genders in the series. The dude is some rail-skinny anime jagoff, I took one look at that weiner and opted to play as the pirate girl instead.
                                Naughty by nature

The one really major new addition here is two-on-two battles, though these aren't really woven into the main story with the exception of one pair of gym leaders. Mostly they just exist in the form of optional trainer battles along the way. There's also a fairly new substantial side game that involves entering your Pokemon into pageants. The Pokemon now have personality ratings in things such as "Cool" and "Smarts", and each of their moves is also tied to one of these characteristics. You attempt to win pageants by setting up the right move set and feeding the little monsters Pokeblocks, which are made from berries you find growing along the way and up their various personality characteristics. It's not a bad addition as it's totally optional, but is more than a bit grindy, and also is somewhat restricted for solo players as you can't make the best blocks without someone else's help.

It's definitely not original, and the story mode is too easy (and becomes unbalanced to Water-type enemies and environments in the later stages , meaning that for 10 to 15 hours straight there's no point in having anything but an Electric type sitting in your lead position). But it's certainly well-crafted, and the focus with Pokemon games is always on the multiplayer anyway. The story mode is long enough and rich enough in exploration and secrets to make it a substantial addition to what was always primarily intended as a competitive head-to-head game first and foremost.

So, which version is the best to have? Unlike with the Gameboy entries, there isn't so much of a clear advantage to the final release (Emerald). It's the most technically complete of the bunch, but the new additions are less substantial than the ones that Platinum offered over Gold and Silver. Unless you really need the minor twitchy battle animations, all Emerald really brings to the table is the ability to catch both of the legendaries in one game (plus the addition of one new one) and a few new optional areas.
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