I acually want to test Altaria GE out. Gallade has problems with it, and even Magmortar has problems, though it is a primary Gallade counter. Look. -20 damage from Resistance, -30 for it's second attack, -10 from Drake's Stadium = Gallade has to flip four Prizes to OHKO it. And don't say Sonic Blade, Unown G stops it. I MAY try it with Darkrai/Dugtrio CG/Weavile SW, Weavile makes him Dark and speeds up Energy, Darkrai adds at least +30 to his 60 attack and Dugtrio stops Magmortar from sniping (this means that Fireball Bazouka does absolutly nothing). Also, Mag X can then only use either Flame Bluster, which only does 60 to Altaria, or the only viable attack choice, Mag's first attack, and I might add in a Beach or two. So, acually, Mag and Gallade may have a hard time dealing with it.
Gallade has to flip over 4 Prizes to KO Altaria, no matter how you look at it. Whether it means one-shotting Altaria, two-shoting, whatever, because Altaria REDUCES damage. Here's a table of how much damage Gallade can do to Altaria with Psychic Cut, with Drake's Stadium in play:
0 Prize Cards flipped = 0 damage
1 Prize Card flipped = 20 damage
2 Prize Cards flipped = 40 damage
3 Prize Cards flipped = 60 damage
4 Prize Cards flipped = 80 damage
5 Prize Cards flipped = 100 damage
6 Prize Cards flipped = 120 damage
As you can see, after Galade has KOed one Altaria, he becomes quite useless. So, then they bring up Gardy X? Well, there is a problem. I have already hit Gallade for 90 at least. This means they are forced to use Psychic Lock, unless they want to give me a free Prize. Psychic Lock will only do 30 damage to me. Not going to make a difference. So, really, I think Altaria has quite a good matchup against G&G.
Now, looking at Magmortar might seem a little ambitious, but, they really only have one viable attack once you get det up. Fire Blast. Beach hurts it severly, however, so this becomes harder to use. Delcatty ex might spell trouble though, doing 100+ damage will kill Altaria. However, Altaria then comes up to take 2 Prizes. Really, Altaria has a pretty good matchup against Fire TRUK too.
Remember, this is purely speculation. It is untested, but it looks good on paper, but I don't know how well it will really do. It just seems to totally losk down G&G, which is the most popular deck in the format. I am just trying to come up with something new, so yeah.