Given that I've just picked up Platinum, I think it's fair to revive this thread.
Now, I started with Red/Blue all the way back in '98. Actually, prior to its arrival in the States I read an article in Nintendo Power about Pokemon as a craze in Japan that was coming to our shores...it seemed obscure, and I wondered whether it could really take hold, but the way NP was describing it it was inevitable that it would.
Over ten years later, it's obvious they were right. Even though I started with Red/Blue, Diamond/Pearl has been my favorite generation thus far. I'm about 3 hours in, and thus far it's not very different from Diamond...though I do like the sleek new Poketch, and I'm looking forward to seeing the changes, however minimal.
Since I always start with a Turtwig (grass types are my favorite), I've decided to start with a Piplup instead. What does bother me about the DP generation is that both grass and fire Pokemon are hard to come by and there's an overabundance of water Pokemon...so I was hesitant to train Piplup. So far, even though he's only level ten, I haven't really had time to regret my decision. I'm training a Bulbasaur in Leaf Green alongside my file in Platinum, so hopefully I can fill up my Pokedex quickly. I do intend to build up a kind of ultimate team and place it in my Platinum file. :3