Steel types are the "best" in terms of defense. Impervious to Poison and has, like, 10 or 11resistances. But not much is weak against it. Skarmory makes it impervious to a previous weakness, ground, but opens up a new one, electricity. But that's good. Basically all that happened was that a weakness changed and it became impervious to another thing. In addition, Steel types only have 2-3 weaknesses.
A balanced type is Electricity. It is also among the best types, and is my fave type. Thunderbolt is a great move, which when used by an electric type (Heck, the only others I know that can use Thunderbolt/Thunder are Starmie [How???], Castform [Wheather], and Zigzagoon [WTF...I taught it Thunder and Surf]) has a general power of of over Thunder's base power, AND has 100% accuracy. Thunder Wave is a great move since, IMO, Paralysis is the best condition (And runner up is badly poisioned from Toxic only). Oddly enough, though it seems the best, frozen is the worst conditon. Almost any fire move and even some other non-fire moves defrost the Pokemon, and there's no move that directly and only induces sleep. Instead, you have attacks with a 1 in 10 or 1 in 5 or something chanes of a freeze. plus, Thunder Wave is one of the only no-cost 100% accuracy moves that inflict paralysis.
As a rule, electric pokemon, being electricity, are generally fast, so if they're down by a few levels, you're fighting another electric Pokemon, or something like Speed Deoxys or other, the pure fact that Paralysis cuts your speed hugely is enough, then the thrown in addition your opponent might not be able to attack. You gain a sheer advantage with faster pokemon. Electric Pokemon are very well capable with inflicting this, as almost every electric move except Shockwave as a 1-in-something chance of paralysis, and that tallies up with a team of electrics and some defense against it's few weaknesses. In addition, Pokemon such as Electrike and Manetric are even farther capable of inflicting paralysis, with not only Thunder Wave and electric moves, but then there's the fact that they have that static ability which works more then one would think.
On my electric Pokemon, I generally run the fastest of them like Jolteon in my party and have Thunder Wave on most of them, Thunderbolt on all if I can get it, Thunder on some just in case against tanks. On most of my Pokemon I have quick attack for a finisher, especially if they get paralyzed but had weakened the opponent way down first.
Holy crap I typed a lot >_>