Sigilyph and Ducklett might be good, but there is no reason to ever find out as long as Archeops exists. The thing is absolutely godly in-game and no flying type can get anywhere near its prowess.
I'm about to enter dragon spiral tower, and here's the team i've got:
lvl 45 Victini
lvl 43 Archeops
lvl 42 Krookodile
lvl 42 Virizion
I was using Gurdurr before I caught Virizion, but anyway, I highly suggest using the pokemon i just mentioned because they rip the game to shreds. I casually sauntered through every gym thus far.
Archeops is pretty bad in-game, it will die to anything, and if not that, it will be crippled.
Because it doesn't get EV trained with perfect IVs, it's not gonna OHKO much unless it outlevels it a few levels.
I still used him, because he does the revenge killing this like no other, and can do nice against things he hits super effectively.
My MVPs were easily Serperior and Lilligant, though. Lilligant because of her incredible power while boosted, and Serperior because it laughs into everything face with its impressive bulk, and eventually with Coil, it can do what Lilligant does.
They really aren't held back by their poor offensive movepool, Lilligant due to her immense power can power through most things unless they quad resist(And those are taken care of by Victini most of the time, who can be acquired really early in the game), and normal/grass gives good enough coverage for Serperior.
Uh, yes, I ran with two pure grass pokes, I just couldn't choose which one to choose since they are both so damn amazing.
My team at the elite four was this:
Serperior
Lilligant
Victini
Galvantula
Cinccino
Archeops.
Serperior and Lilligant are such bosses, that Serperior swept not only the fighting dude, but also the dark dude thanks to coil.
And Lilligant obliterated the ghost one, though had some troubles against the psychic one.
In the end, it was a joke.
A question, though, the roaming genie, does he respawn when you defeat the elite four?
He's the only legendary I haven't caught yet, and when I tried, I was dumb enough to ko him.. Had him trapped with Galvantula, and thought I could take down another sliver of health, but min-max damage screwed me over.