I'm surprised by the consensus that its skipped over, such a shame. I bought a Gym Challenge first edition booster box in 09'. looking back, and its the only complete set I've examined up close. I enjoy how the set has plenty of commons and uncommons to discover, unlike other the usual 64 card sets where the commons and uncommon cards frankly get repetitive.
Koga's Zubat, Blaine's Charmander, Sabrina's Haunter and Sabrina's Gengar are such beautiful cards.