Gen 1: RB
Gen 2: GS
Gen 3: RS
Gen 4: DP
Gen 5: BW
Gen 6: XY
Gen 7: SM (if you've played it)

Personally it goes BW > XY > RS > DP > GS > RB (haven't played SM yet, expecting it to be between BW and XY or possibly above BW)

willing to defend opinion if im called a shitler