I think his legend grew a lot due to the whatif discussions.
We've had great legends like Domazos, Papaioannou, Saravakos etc who accomplished more and also had intense interest from abroad (Inter, Real Madrid, Juventus respectively being the most prevalent) that probably deserve to be considered the greatest. Not sure on the new era guys (2004 generation). Apart from Karagounis and Katsouranis, the next best player wasn't part of the team (Lyberopoulos) and they've all done well in Europe, but they just don't have the allure or the brand name let's say. Also helps that they were robbed of a shitload of domestic titles due to a legit mafia that runs the sport here.
Some other old time greats are Sideris, Mavros, Delikaris, Antoniadis, Nestoridis, Koudas etc.
Hatzipanagis gets love by all because he played for a team that no one really hates, didn't compete for trophies and there's no pride lost in saying that he was better than your legend.
Apart from the Bosman era not being a thing, there never was any success apart from the 1971 Panathinaikos team, just a couple of big tournaments for the NT because the system was different, less countries etc, so they're not popular. But then again, you don't hear much about Feyenoord, Goteborg, Steaua, Anderlecht, Club Brugge, Partizan or Red Star either, so it's more of a modern era reflection thing. People don't realize that the status quo is just 10-20 years old.