Very interesting to see some of the responses!
Personally, here's mine.
6>2>4>1>3>5
I really like a lot of the simplifying that Gen 6 brought to the table. EV training no longer a pain, breeding no longer a pain... Call me a filthy casual, but it made the whole game feel a lot more accessible to me. For the first time, I'm motivated enough to complete the region's Pokedex. I've also enjoyed the clothes-collection spree, and many of the character interactions were nice. I can understand where people don't like Gen 6, due to its deemphasis on the "hardcore" aspects of Pokemon, along with the fact that many towns are never visited ever again for any reason (like Vaniville and Aquacorde, both irrelevant to the point of being outright segregated from the rest of the map).
Gen 4 is solely carried by HGSS. First, my perspective on the negatives... Sinnoh I thought to be extremely uninspired. I remember virtually nothing of that game, nothing of its cities, and I've played through the game three times. It held my attention at the time, but it is absolutely not memorable. I thought the character design was average, the battling slow, and the starters and added Pokemon mediocre... And yes, Johto was a massive level grind. However, on the flipside, what boosted my enjoyment of the Johto games, however, was the sheer quantity of things (towns, trainers, world "space) to explore. Younger me thought it fantastic that I got to see what Kanto evolved into, and that Johto had a substantial "postgame" after the first Elite 4 trip. Years later, when going through HGSS, I still didn't have much of a problem other than the Mt Silver grind. Plus, my favourite starter is from Johto: Cyndaquil.
Gen 1 just feels too old. There were too many glitches and I know they screwed up my save file many a time (as younger me needed to have many Master Balls from the item trick). I never had motivation to do postgame in this gen, though the barebones plot was good enough to keep me interested in completing the main plot many times over. I was much more captivated by GSC's addition to the game's length, as artificial as it may have been.
Gen 3... Ehh... It's hard. I liked RS's plot, the little things like the Wally quest, how you actually battle your dad, and how you helped the other team maintain normalcy. I hated the sea, the abundance of legendaries, the irrrelevance of Professor Birch. My second favourite starter is from Hoenn (Torchic). In contrast, I thought FRLG to be an affront to the source material. Sprites seemed off, Sevii Islands wat...
Gen 5 was just...no. I played both Black and Black 2; I couldn't finish either. Got to Skyla in both games and gave up. They remain the only Pokemon games that I haven't finished to date, though I will probably try to soon, due to Bank. I didn't like many of the new Pokemon either, and I thought the cover legendaries were pretty bleh.
