>>47834760This is kind of my specialty
>is hardestBW2 has the potential to be the hardest when you play with challenge mode. USUM is overall not hard but has the best boss battles with good strategies. Platinum is probably the hardest overall but most of that isn't even due to actual strategy, it's due to enemies carrying coverage moves that you wouldn't normally expect and especially in cases where the move is on multiple party members or earlier in the game when you can get the move. That and RNG makes Platinum kind of artificially hard but it just comes down to luck and grinding. This was kind of the them for all of Gen 3 and 4 and it stopped in BW for better or for worse. BW2 and USUM require a bit more of actual strategy at times.
>has best designed pokemonOverall, BW does. I think that other games arguably have equal or somewhat better Pokemon, but BW wins while having quality and quantity. Honorable mention to Gen 1 and USUM.
>has best designed map and regionBW2, followed closely by HGSS and Platinum. XY is also pretty good at this too.
>has best soundtrackReally I love the soundtrack on all of the games, but for me SM/USUM take the cake.
>has best plot and charactersUnironically, a tie between ORAS, and USUM. ORAS if anything handled this part really well by fleshing out the setting of Hoenn and its lore without needlessly overcomplicating it and USUM did the same. USUM did sacrifice some character development but traded it off for development of other characters and one of the best extended plots of the series. Honor roll goes to HGSS and BW/BW2.