Platinum Pokédex
The native Sinnoh Pokédex in Pokémon Platinum expands upon that from Diamond & Pearl, with 210 total Pokémon listed. It adds Rotom, Giratina, the whole Eevee line and new evolutions for older Pokémon like Dusknoir and Tangrowth - although it still omits some Sinnoh legendaries.
After seeing all 210 Pokémon the National Dex can be obtained, with the entire set of Pokémon in the order they were added. See also: the Diamond/Pearl/Platinum Pokémon stats page for just the new Pokémon introduced in Gen 4.
Kricketune
Bug
Misdreavus
Ghost
Hippopotas
Ground
Tentacruel
Water · Poison
Lickilicky
Normal
Electabuzz
Electric
Electivire
Electric