We don’t expect Steelix to shine or to be very powerful in the new Generation.
New Gen 2 Evolutions
Zubat -> Golbat -> Crobat max CP 2348
Onix -> Steelix max CP 2080
Scyther -> Scizor max CP 2270
Horsea -> Seadra -> Kingdra max CP 2671
Porygon -> Porygon2 max CP 2653
Chansey -> Blissey max CP 1234
New Gen 2 Pre-evolutions (Baby Pokémon)
Pichu max CP 426 -> Pikachu -> Raichu
Cleffa max CP 599 -> Clefairy -> Clefable
Igglybuff max CP 612 -> Jigglypuff -> Wigglytuff
Tyrogue (*) max CP 550 -> Hitmonchan OR Hitmonlee OR Hitmontop max CP 1515
Smoochum max CP 820 -> Jynx
Elekid max CP 1166 -> Electabuzz
Magby max CP 1270 -> Magmar
New Gen 2 Split-Evolutions
Oddish -> Gloom -> Bellossom max CP 2394
Poliwag -> Poliwhirl -> Politoed max CP 2460
Eevee -> Umbreon max CP 2311
Eevee -> Espeon max CP 2252
Slowpoke -> Slowking max CP 2597
(*) Tyrogue note: With the addition of Tyrogue, who has a split evolution between Hitmonchan, Hitmonlee, and the new Hitmontop, it’s likely that Hitmonchan and Hitmonlee candies will be merged.
A word of advice
We advise to save Candy for all types of crossover evolutions, including Pre-evolutions. As you can see, some of the Pre-evolutions increase the Max CP of their evolved forms (Magby!).
It is also possible that some move sets will only be obtainable when evolving from a Baby Pokémon, so that is another consideration to keep in mind.
Especially, think about stocking up on Porygon Candy via walking him as your Buddy. Porygon2 is going to be very rare, probably the rarest Pokémon on this list.