SKBRDVR1:
'Best" is definable in many ways. Having spent a good deal of time on a lot of wrecks off the NC/SC coast, I think they rank at the top of the list. I'm sure Bikini Atoll would be more interesting, but we've got everything from the Queen Anne's Revenge (Blackbeard the Pirate) to German U-Boats to modern reef wrecks. However, be aware that our conditions are not the best sometimes. You may have a long boat ride (sometimes 3-4 hours) to get to "snotty" conditions. There are a lot of "cattle" boat operations. Riding 3-4 hours with 20-25 puking maniacs is no fun!
The wrecks still give up booty. If you can get a charter organization to run you on a 6 or 12 pack and you can get sell the whole boat, then you're all on the same sheet of music and typically the dives are better.
My vote is a "go" for the NC/SC coast
I gotta agree with SKBRDVR1.
The great lakes has beautiful wrecks, many of them older wooden wrecks, and nicely preserved. But the freshwater wrecks do not offer the same amenities as those off North Carolina, when diving in or near the Gulf Stream. The water can be in the 70s and 80s, a deep crystal blue. The vis can be up to 100' or more. There are sharks, rays, large turtles, sunfish (mola mola), schools of baitfish so dense they obscure the wreck, and huge pelagic fishes who inhabit the wrecks. While hanging on deco stops, we've had a pod of dolphins swim around us for over 20 minutes, perhaps 30-40 of them darting in all directions. The diversity of life on the wrecks in the Gulf Stream is unparalleled in my experience, and you can enjoy wreck depths from 60'-70' down to the E.M. Clark at 240' in the same conditions.
I've dived wrecks off Okinawa, the Philippines, Guam, Palau and Peleliu in the South Pacific, the Great Lakes, and Florida's east coast...and the east coast wrecks that lie in the Gulf Stream are simply world-class if you catch them on a day when the weather cooperates. Additionally, many of them have tragic history - you can dive a tanker that was torpedoed one day and the german submarine that killed her the next day. They are real wrecks, not artificial reef wrecks, and they offer diverse challenges.
For my money, the wrecks that lie in the Gulf Stream off North Carolina - on a good day - are among the finest wreck diving on the planet.
YMMV.