GP2 is closer to F1 than F3000 ever was and is simply a better platform for young drivers to get into F1. If I remember correctly, then F3000 engines had about 400 HP-s, but current GP2 engines have 600 HP-s. F3000 cars lost about 20 seconds (depended on circuit) to F1 cars per lap, the loss of GP2 cars is about half of that. So... without any doubt GP2 is a strong series and who is successful there, tends to do well in F1, but most of the F3000 champions never achieved the predicted success in F1 (if they even participated).