I recently finished playing through Crystal which was very fun indeed. I had a close match against Lance which was neat. Right now I'm training up a Hitmonchan to replace my Raticate (which has proved to be grat until Lv. 50 but starting to suck ever since he starts to climb in level from there). Also I'm looking for something to replace Sudowoodo with, maybe a Dark type like Umbreon or something that can inflict a lot of statuses.
Currently I have: Meganium, Skarmory, Sudowoodo, Raticate, Slowking (which is a weaker Slowbro whose higher Sp. Atk. doesn't come in handy, but I like it and it's decent) and also last but not least Nidoking (which rocks my socks).
For some reason I like Raticate in RBY but not in GSC that much. I can't really tell why though. :/ Maybe it's the sprite or something?