the whole point of Black and White was that the new Pokémon had NO link to the old ones, so it felt like a new experience again :)
Some of the Unova Pokemon share relations with the older ones:
-Snivy, Tepig Oshawott = Kanto, Johto, Hoenn and Sinnoh starters (starter Pokemon)
-Patrat line = Rattata, Sentret, Zigzagoon and Bidoof lines (regional rodents)
-Pidove line = Pidgey, Hoothoot, Taillow and Starly lines (regional birds)
-Roggenrola line = Geodude line (common Rock Pokemon that reach their final forms by trading)
-Woobat line = Zubat line (regional bats that reach final forms through happiness)
-Drilbur line = Diglett line (moles)
-Audino = Chansey (seen with Nurse Joy in the anime, have massive HP and reward a lot of EXP when defeated)
-Purrloin line = Meowth, Skitty and Glameow lines (cats)
-Munna line = Drowzee line (tapir-like Psychic Pokemon that are associated with sleep)
-Timburr line = Machop line (Fighting Pokemon that reach their final forms by trading)
-Tympole line = Poliwag line (tadpoles/frogs)
-Throh/Sawk = Hitmonlee/Hitmonchan (Fighting Pokemon that appear to be related to each other)
-Sewaddle/Venipede lines = Caterpie/Weedle/Wurmple lines (Bug Pokemon that appear early in the game and in forests)
-Maractus = Cacnea line (cacti)
-Scraggy line = Croagunk line (similar appearances, part Fighting type)
-Tirtouga/Archen lines = Omanyte, Kabuto, Lileep, Anorith, Cranidos and Shieldon lines (fossils)
-Trubbish line = Grimer, Koffing and Gulpin lines (2-stage Poison evolutionary line)
-Zorua line = Riolu line (evolved forms debuted in movies prior to their generation, even though Zorua was introduced along with Zoroark, and Riolu was not introduced with Lucario)
-Gothita line = Ralts line (reason to be confirmed at some point)
-Solosis line = Abra line (3-stage Psychic evolutionary line)
-Ducklett line = Psyduck and Wingull lines (2-stage Water bird evolutionary line)
-Emolga = Pichu line, Plusle, Minun and Pachirisu (Electric rodent)
-Foongus line = Paras and Shroomish lines; they are mushrooms. Also the Voltorb line because it resembles a Poke Ball
-Frillish line = Tentacool line (jellyfish)
-Joltik line = Spinarak line (spiders)
-Ferroseed line = Pineco line (stationary Pokemon with high Defense, but low Speed)
-Klink line = Magmemite line (3-stage Steel evolutionary line)
-Litwick line = Gastly and Duskull lines (3-stage Ghost evolutionary line)
-Axew line = Trapinch line (final forms commonly mistaken for pseudo-legends)
-Cubchoo line = Teddiursa line (bears)
-Stunfisk = Dunsparce (derp-ish Pokemon)
-Mienfoo line = Mankey line (mammalian 2-stage Fighting evolutionary line)
-Heatmor/Durant = Zangoose/Seviper (rivals)
-Deino line = Dratini, Larvitar, Bagon, Beldum and Gible lines (pseudo-legends)
-Legendary musketeers and legendary Kamis = Legendary birds, legendary beasts, Regis, lake trio (legendary trios)
-Reshiram/Zekrom = Lugia/Ho-oh, Kyogre/Groudon, Dialga/Palkia (version mascots)
-Meloetta = Shaymin (legendaries with 2 forms)
-Genesect = Mewtwo (Pokemon created through genetics)