Lanturn and Manectric are good Electric-type options. However, Lanturn comes only after you get Surf as a Chinchou in Routes 124 and 126. It does evolve quickly from where you obtain it and gets a good STAB combination. But it does require grinding though, so does Electrike even though it's obtained early-game. Both have slow growth rates, so I'm not telling you to use those.
Its movepool is mediocre and it is outclassed by Manectric offensively, unless you get a Light Ball one. Even with a Light Ball, Pikachu will be KOed by a light breeze.
Its very fast, but its also rather weak and easily walled.
Slow with a shallow movepool, but has good typing. Magneton is pretty strong and its typing is very useful against the Elite Four.
Among these options as well as those Smoothie said, Magnemite is a really good option. A part Steel-type grants its many useful resistances, and I think that's better than any of the other two. Voltorb's stats are average except for its Speed, and Raichu is really frail. None of them are as helpful as Magneton against the Elite Four, except perhaps the Champion Wallace.
Magnemite gets Spark at Level 26, which isn't very far from where you get it. Spark allows it to deal with most of Winona's team. Apart from that, its typing is helpful vs Elite Four, with it dealing with Sydney, most of Phoebe's team, Glacia and Drake's Altaria. Besides, it's also good against most of Wallace's team except for Gyarados with Earthquake and Whiscash. I recommend this set:
Magneton @ anything
- Thunder Wave
- Metal Sound
Although it's movepool is really shallow, it doesn't need anything else to be more helpful.
Hope this helps :)