>>58802182as far as im concerned, gens 1 and 2 are the "true" classic era (since they were directly linked + before most of the recurring design tropes were established) but just the 151 are the "classic" dex (they're just the ones EVERYONE knows, not to say the gen 2 dex is bad or anything, i actually quite love it.)
in my mind, i separate the gens into 5 eras:
>1-2: classic era>3-4: golden era>5: transitional era>6-7: 3ds era>8-9: dark age 
