This isn't so much what definitely are the best Console Generations, but rather how you'd rank them personally. Just a reminder of what each console generation contained.
First Generation: Pong Consoles
Second Generation: Atari 2600 and 5200, Intellivision, Odyssey 2, Colecovision, Vecrex, Fairchild Channel F
Third Generation: NES, Master System, Atari 7800
Fourth Generation: SNES, Genesis, TG16, Neo Geo AES, CDi
Fifth Generation: PS1, N64, Saturn, 3DO, Jaguar, Genesis Add Ons
Sixth Generation: PS2, XBOX, Gamecube, Dreamcast
Seventh Generation: PS3, Wii, 360
Eighth Generation: Wii U, Switch, PS4, XBONE
Here is how I would rank them
1. Gen 6: Two of my top three game consoles of all time are part of this generation (Dreamcast and PS2). On top of that, the amount of insanely great games from this generation seem uncountable. I also would argue that gen 6 gave birth to modern video game culture which continues to this day.
2. Gen 5: This was the generation that got me really into gaming, and my absolute most cherished memories of video games come from this time period. On top of that some of the best games I've ever played are from this generation, along with one of my favorite consoles, the N64.
3. Gen 8: Our current gen, I haven't had as much fun as I've had this generation in years (since gen 6). Some of the best games I've played came from this generation, and also the amount of hype and excitement I've had for various games throughout this generation might be unmatched.
4. Gen 4: This was my entry point into gaming and I still have many find memories of gaming during this period of time even though I was very young. Some of this generation is hard for me to get into these days, but quite a few games still hold up. I still enjoy revisiting games and consoles from this generation regularly.
5. Gen 7: I really enjoyed Gen 7, although for whatever reason it just doesn't have that same impact of specialness that any of the generations above have. It had a lot of good games, but few of them felt truly amazing like all the previous generations I mentioned. As time goes by it becomes harder for me to appreciate this generation, but despite that I still really enjoyed it and still enjoy it.
6. Gen 3: Gen 3 was just before my time, even though I was born during the midst of it. I never owned a gen 3 console until many years after it was over, but did play NES at various points when I was a kid. I definitely don't undermine the significance of this generation as it's the one that gave video games new life after the gen before it, but on a personal level it just doesn't do a lot for me.
7. Gen 2: I literally have no memory of this generation and have never owned a console from this generation. I have played some 2600, but the games are so primitive that it's nearly impossible for me to get into any of them.
8. Gen 1: Pretty much the same as Gen 2, except this generation is pretty much just pong consoles which makes it even less appealing. Not that pong is a bad game, but the lack of variety and also given how simplistic it is makes this my lest favorite, least appealing generation of video games.