Objectively speaking,
6 > 7 > 5 > 3 > 2 = 1 >>>>>> 4
The games have had an almost linear increase in quality of life and mechanics, with the following exceptions:
1. SM's poor framerate and inferior online inferface put it a bit below ORAS in terms of quality, but by the end of the generation I expect gen 7 to surpass gen 6 overall.
2. Gen 2 had HUGE improvements over gen 1 in many areas but was unfortunately just a chore to play compared to gen 1 due to its bad new Pokemon and terrible region layout, so I'd say they're roughly on par.
3. Gen 4, while bringing a few good things, is unquestionably trash. The godawful engine, sub-Johto-tier region design and halfassed Physical/Special split make this generation the most desperately in need of a remake. While gen 5 did very little to innovate, this is because it was dedicated almost entirely to fixing gen 4's mistakes.
These facts are unpopular on /vp/ due to the board's population, which is mostly composed of children who grew up with gen 4 or 5 as their first games. Still, facts are facts.