i played Pearl and Platinum. Platinum definitely fixed some of the problems, but it is still flawed.

All solid games for me, but the ones I've played from best to worst is:

1. Ruby/Sapphire (Gen 3)
2. Fire Red/Leaf Green (Gen 3?)
3. Black/White; Black/White 2 (Gen 5)
4. Diamond/Pearl; Platinum (Gen 4)
5. Heart Gold/Soul Silver (Gen 4?)
6. X/Y (Gen 6)
7. Sun/Moon (Gen 7)
8. Red/Blue; Yellow (Gen 1)
9. Omega Ruby/ Alpha Sapphire (Gen 6?)

How can you rank Ruby/Sapphir first and them Omega Ruby last?

I will rank it at how they impacted me and how I remember them

1) Gold/Silver :most gameplay addition, huge content, breeding, Lugia
2) Ruby/Saphir: Pokemon contests, climate, double battle, great region and legendary, talents
3) XY Good region, mega evolution, fairy addition, greant competititive online game, Super Training
4) Black/White Great story, totally new Pokemon and different region
5) Sun/moon, average region in comparison of the other, but some interesting change to the formula
6) Blue/Red, the first one, it was amazing for that time, but the other games are just better after. I will always remembrer it as I played as a kid.
7) Diamond/Pearl: Just forgettable for me, not bad, but did not impact me, and these legendary pokemons are just bad. It added nothing special.

I'm quite surprised to see many people list my least favourite Gen as their favourite. I suppose it comes down to what you want out of the Games. 

1) Gen 7 - The change in structure to the game worked well, and whilst I can't be doing with the Z move animations, I believe many of the new Pokemon work extremely well and give loads of different options to experiment with in terms of battle strategy. The world and variety of New Pokemon are both well suited to each other.

2) Gen 4 - This is influenced by this is where I really started to understand the battling mechanics, which made the games so much more interesting for me. Adding to that the new hardware gave the developer greater scope for environmental variety. I'm still hoping for a remake on the Switch. Admittedly though, the slow pace of the battles is very grating when I try to revisit them.

3) Gen 2 - Builds on Gen 1. Pretty much the same as the entry below.

4) Gen 1 - I game I cant help but look through with nostalgia glasses. Even 20 years on, the game still holds up for me, shown by the  virtual console release. Yes, its basic by modern standards, and the Lets Go remake highlight how shallow it is in terms of features, but I think the classic version suits it better. There is more of a sense of adventure in it from this angle.

5) Gen 6 - Another one I really enjoyed at the time, but was completely shown up by Sun and Moon. Early on in the game it really seemed to lack and identity, with a fairly bland feel. This did disappear gradually, but it did feel like the developer was just finding their feet on the new hardware. 

6) Gen 3 - An entry I enjoyed very much back in the day, but when weighed up against other entries is just feels shallow by comparison. There's nothing I really hate about it, just a lack of things that push it on.

7) Gen 5 - This Gen brought next to nothing new to the series. Its main selling points are the revamped graphics to better utilise 3D, and the strongest storyline in the series. However, neither are really the main draws of the series. It also has some of the worst Pokemon designs ever, featuring the embryo Pokemon, afro Pokemon and ice cream Pokemon. Also many look like direct stand-ins for Gen 1 Pokemon, so it all just stank of lack of ideas and/or creativity. 

Is interesting to see other people ranking my favourite last and vice versa. I think it just shows how people enjoy different elements of the series, especially with a few people going for the unapologetic collectathon that is Lets Go - one that I find rather tedious.

Ignoring remakes:
Gen 2
Gen 5
Easily the best two, followed by:
Gen 3
Gen 1
In Gen 1's defense, it really hasn't aged well.

The rest were just too damn boring. Didn't even finish Y (7 badges) nor Moon (I don't know, my all bird team had levels in the high 30s I think). Diamond was so boring that I barely remember what happened in the game.

My ranking for every game:
Platinum > Black2/white2 >Black/White > Heartgold/Soulsilver > Omega Ruby/Alpha Sapphire > Emerald > Ultra Sun/Moon = Sun/Moon > Diamond Pearl > Ruby/Sapphire > FireRed/LeafGreen >Gold/Silver/Cystal > Red/Blue/Yellow > X/Y