I'm gonna say Gen6 is my favorite, just because how cool online is.
Fun battling with strangers, fun trading with strangers.
Gen1 is a close second. I just loooove the trick where you glitch the game by teleport/flying away from a trainer fight. Lv7 Mew before 2nd badge!

What? Omega/Alpha perfected gameplay:
Fly by poking your map
Fly to routes and caves, not just towns
Breeding area @ Battle Resort, OP
See what pokemon are in your area/if you've captured all in the area by looking at your bottom screen
Find specific pokemon in that area with DexNav search & slow walking
See what berries are ready to be harvested by checking Pokenav
See what trainers are ready to be refought by checking Pokenav
There's like 15 legendary pokemon to catch
If you lose to a legendary, they don't disappear [Kyogre anyway]
You can get a bunch of custom pre-made trainers in your secret base to farm MAD exp off of for quick teambuilding (5 trainers of 3x Lv100 Healing Wish Suicide Blissy's)
Uh, hello? You can literally fly. How cool is that? Too freaking cool.

Customizing your character was neat though. It made your online avatar a little more unique. I miss it, too.
Not enough to ever go back to X/Y though.

This, and it is what i voted for

Next is gold silver

am I blind? where the fuck is blue? or even generation 1?

he listed the gen 1 remakes in their place

Gen 1 for sure

2

Gen 1 (Fire red, Leaf green)
Gen 2 (Soul silver, Heart gold)

Lolol but in all honesty its gen one red version for me first time I played it I was hooked at like age 7 lol good old days

Invested too much time in all gens and loved it too much to isolate a gen to prefer.
For the poll I will say Gen 6, cuz of the comps I own there and the graphic.

And some of the 1