Atm, all are level 57 because I'm a stickler for equality in their levels, even if it takes a butt-load of time to keep it that way
Garchomp (raised from egg)
Torterra (raised from egg)
Rapidash (raised from egg)
All around, I love the team. The only one I'm iffy about is Rapidash just because his (well, her) defense is so low, along with mediocre hp and a REALLY BAD learnset. But, hey it's the only fire type in the game before the national dex. And I wasn't about to get a flaming monkey as my starter.
Empoleon is great. Can take a lot of hits and has a lot of versatility. I got Torterra by trading my Palkia for a Turtwig via GTS (I never liked using legendaries tbh, I just get for the 'dex)
Garchomp is a stud without a doubt...accept against Ice
His hp, attack, and speed are all stellar.
Staraptor is an attack god. I can't believe how powerful it becomes after being a tiny little Starly in the beginning. It one-shots practically everything it touches.
Luxray is great as well. With it's high attack, I'm pretty sure Thunderfang is actually more powerful than Thunder.
I already beat the elite 4 with this team, minus Garchomp and Torterra, when they were all 53. I got worked by the champ though.
Their movesets are pretty much all offense.