Let's see...
Gen I: 7/10 For what it was, on the platform it was developped on. Kudos. I remember playing a lot of it back in the day.
Gen II: 8½/10 GenII was probably the Generation I played the most on. I used to have a full 250 pokemon pokedex captured. Celebi was the only one missing of course. Until recently, my Gold cartridge's battery died and the pokedex along with it.
Gen III 6/10 GenIII is the generation I have the lest memories on and I don't like it that much. The new pokemon of that era were meh and the moves too.
Gen IV 9/10 GenIV is when I really got back to pokemon in my college days! Lots of good memories. I really liked the new pokemons, the moves and the region too.
GenV 5/10 My least favorite generation. Gen V could have been what Gen VI is. "The 3DS has a low userbase". Bullcrap reason. Bringing pokemon sooner to 3DS would made the console launch to what it is now sooner. Anyway, the only thing I like to BW was the story. Beside that, the fact I was forced into using new pokemons... I didn't really like it that much. B2W2 was a cashcow and soul less release for the most part. I don't own these games.
Gen VI 9½/10 So far, the best gen. The new 3D environment instead of sprites, animations, the new region, the new type... it's all goodies. And I feel that the general reaction to the game is what the reaction was for the original.