I wanted to do this, but just with my own format. I'm going to go in order of the main-line games and give each a grade that way. For me grades are based on when they came out as opposed to playability now. I was writing some about music at first, but I then realized literally every release has top-notch, fantastic music, so I just left that out:

Red & Blue: A : fantastic games for their time that started everything off

Yellow: C : Pretty cool to have Pikachu follow and definitely had hype, but not enough different from originals

Gold & Silver: A : Two regions were amazing, color advancements, etc

Crystal: C+ : This game would grade as good and GS on its own (it is the version I have on VC), but as a new title it just didn't bring enough new to the table, but a little more than Yellow did

Ruby & Sapphire : A- : I love the new region, the new graphics are outstanding

Fire Red & Leaf Green : A : I think these were great for the first remakes. Sevii addition is great, only complaint is can't use Hoenn/Johto Pokemon before post game (but I get why they did it)

Emerald : B- : Battle Frontier is cool addition, but still not a lot different (still the version I play now though/best Gen III Hoenn version)

Diamond & Pearl : C+ : These are great games in general, but they honestly don't play well (slow, music issues, etc). Only old games I don't play anymore. Just wasn't a smooth transition to DS

Platinum : A- : Fixed the issues of DP and good additional content, still pretty similar, but this is the Sinnoh game I still play

HGSS : A+++++ : Best game ever, everything was fantastic, content, graphics, follow, remixes, perfect combination of remake and new stuff

BW : B+ : Great games, great story, but it was also kind of daunting for me with no old Pokemon so that impacted my experience

BW2 : A++ : Just 2 + to differentiate from HGSS, but this is the first second version with new story and it was amazing, plus loads of postgame content, I've still found new stuff in the postgame recently(ish)

XY : B+ : I think Z might have been a more complete game, but still a lot of good memories, great region, and a great transition to 3DS, postgame sparse, beginning of Game Freak giving less effort imo

ORAS : B+ : I love these games, but just not enough new to me as compared to previous remakes to get an A

SM : A- : Fantastic in-game story, fantastic region, biggest complaint here is just not enough content (really quick to get around)

USUM : B : I love the additional content, but like other 3rd versions still too much similar to SM, also the story (although similar) was better in original SM

LGE : C : Only played Eevee (because I love Eevee) Very cute in many ways, but the game did drag on for me some. I was hoping for Kanto map to be a little more advanced/sized better in this game.

SwS : B- : Great game, also loved the DLC, but too much was missing. Too many buildings you can't explore, too many really short routes, just seems like general effort was less in this game (problem that really began in Gen VI, but was too apparent here), postgame wasn't great (until DLC), don't do much online since I only have had the paid service for a small period of time

BDSP : F : Caveat - Never played this - but this is literally the only Pokemon game I have never played and there is a reason for that, it looks god awful, seemingly very few improvements (less content than Plat?) overrworld is one to one, I saw literally no reason to get this game and still don't. Even two years ago to imagine I would ever not play a main-line Pokemon game is crazy to me, so for this game to be so disappointing I didn't even considering buying it I think an F is quite fair.

LA : A+ : One of only 3 to get a + after the A, I just love this so much, what a daring choice to go a totally new direction and I think it was so on point. I saw some game reviews bumped it lower for the actual region, but I think it was fantastic, and I love the foreshadowing and little hints. I hope we get more games either like this or more totally off the wall attempts like this! Only minor complaint is the postgame is pretty small, I think there was an opportunity to explore new areas postgame.

SV : A : I played Scarlet, only realized recently there are some semi major differences and I'm really glad I chose Scarlet. The region is absolutely amazing, with my only complaint being there aren't enough trees or thick forests (I'm a huge forest fan irl). I really love the in-game story, the in-game characters, and what I have done of the postgame so far. The crater stuff was super interesting, but again I played Scarlet, that Violet version of that doesn't seem as cool to me. Hoping there is DLC as well, but so far I really am happy with this game, was very surprised to see it got poor ratings, I think it far exceeds SwS. I love the size of the region with so much to explore and so much natural beauty.

The only non-main series game I have played extensively is Super Mystery Dungeon. I would give that game a B+, it is a very fun game and had all 721 Pokemon, a fun story, etc. Actual dungeon gameplay can get repetitive, which lowers the grade slightly.