Greece captain Giorgos Karagounis believes the delight of reaching the the Euro 2012 quarter-finals rivals that of winning Euro 2004.
The midfielder scored the winner as Greece stunned Russia 1-0 to finish second in Group A.
Karagounis is banned for the next game but told Greek television: "I thank God for letting us celebrate such moments.
"We did not give up. We can compare this to our cherished moments in Portugal in 2004."
Karagounis was booked for diving when it appeared he had been clipped by Sergei Ignashevich in the Russia box and the yellow card rules him out of a last-eight meeting with the Group B winners.
"We believed all day that we would not return to Athens [after the group phase]," added Karagounis, who won a record-equalling 120th cap for Greece against Russia.
"We kept our promise to all. All Greeks can now celebrate. When we are united no-one can stop us."
Greece manager Fernando Santos put his side's win over Russia down to their determination.
"Focus and concentration decided this match," said Santos, whose side drew with Poland in their opener before losing to Czech Republic.
"We didn't allow our opponents to exploit their strengths and score a goal.
"The character of the team emerged when they were in this situation and the reply was fantastic.
"[Russia] need a lot of space, especially in the last third of the pitch in order to create dangerous chances.
"So we needed to be very concentrated in not allowing them to deploy their skills and the talent they possess."
He added: "From tomorrow we have to clear our minds and keep our feet on the ground. We know who we are, and we will give everything in the following match as well."
Russia coach Dick Advocaat blamed his side's profligacy in front of goal for their defeat and exit from the tournament.
"We should have won by a wide margin but we didn't," he said. "My compliments to Greece.
"A number of players weren't sharp enough to score. We did go forward, and were very attacking. We played well, but you have to score goals.
"We did that in the first game and, despite all the possession, we didn't do that [against Greece]."