Worst, B2 for being the same as black, which I was already sick of and spent 500 hours on. That or Pearl, while there were some good things about it the whole experience was kind of boring.
Best for me was White/Ruby/SS, White for having the best story and epic legendary, Ruby because of nostalgia + they were good games with cool legendaries theme and pokemon, and SoulSilver because I can't think of a single thing they messed up there. Except the slow battles. There might have been a level curve, but I didn't notice it. Pearl made it look good in comparison, honestly.