>>35871928Platinum is a more rural, snowy region than Hoenn. Great locations and great music, though the engine is really slow. Has 107 new 'mons.
Heart Gold and Soul Silver are pretty good remakes of Johto. Includes almost everything that was added in Crystal, brings back areas of Kanto that were cut in the original Gen 2, probably the best remakes Pokémon has.
Black and White are an attempt to bring back the feeling of discovery in Gen 1, with no old Pokémon appearing until postgame and more than 150 new ones. Got a huge backlash at release from people who think classics like Pikachu are essential, so they made Black 2 and White 2 after which mixed older Pokémon into the region and added a lot of new areas to expand the region, plus some great features like Join Avenue that you sadly can't fully enjoy now because online play is needed to fully expand them.
X and Y are not very good games. The region is really empty in terms of things to do, the pacing is very strange with the trek from Gym 1 to Gym 2 being one of the longest stretches in the franchise but then everything after rushing through at lightning pace, and the rivals are all overly-clingy "friends" who never leave you alone. They're also the only games to never get a third version.
Omega Ruby and Alpha Sapphire are the worst remakes in the series. It has nice ideas and a cool few features like Dexnav (you can see Pokémon in the overworld with special moves/abilities/etc. and sneak up to encounter them) but almost nothing from Emerald is there, some areas in Hoenn are butchered, music sucks, and this annoying bitch Zinnia is introduced who completely hijacks the plot.
Sun and Moon, and by proxy USUM, are one long cutscene occasionally punctuated by a battle. Avoid unless you've played every other Pokémon game and are REALLY curious.
I recommend playing HGSS if you want nostalgia, Platinum if you want something close to Gen 3, and BW1 (followed by 2) if you want something fresh.