The Justice League Europe run was the original Ralph/Sue combo series for our generation. FKATJL was hilarious in its own right, but, there's more JLE material than a six-issue mini. That's my suggestion for the Sue/Ralph duo.
Also, didn't Meltzer say that in this series, Ralph would be at the forefront of the investigation? I rememeber the hype in all of these interviews that Ralph would take center-stage for this story. Well, where the hell is he?
