1. HG and SS
Without doubts my favourite Pokemon games. I loved all the features, graphics were GREAT and Pokemon followed you. They also enhaced the game a lot, so it was more fun to play it than GS.
2. White and Black
I really liked them as well. The only problem was....it was too easy for me.
Playing it was a lot easier than DPPtHGSS and RSE. I hope that Gray makes it harder.
3. Diamond and Pearl
I really love the Sinnoh region and its Pokemon. Also, PMD Time and Darkness are my favourite Pokemon games counting Spin-Offs.
4. Platinum
Pretty much DP, although it was harder, i didn't like that they changed the sprites (They were uglier for me) and it was a really mere third game compared to Emerald.
5. Emerald
A quite fun game still, but after Lilycove i got depressed with it. The endless seas were a really bad idea, and it was a bit weird. I did like, however, that it expanded RS really well.
6. GSC
Basically HGSS, but without many neat features. I also don't care about nostalgia, and i just prefer the newer version.
7. RS
Emerald, but without many good features.
8. FR
I didn't like it. It was a quite good remake, but it just resembled RBY too much. It was also quite easy and dull.
9. RBG
I hate Kanto. It was a sad, dull place. The plot wasn't entraining, too.
10. Yellow
As much i hate anime, i hate yellow. That's all about it.