The 73-year-old thinks that La Roja deserved to finish at the top of the group and says that only Germany have been better at the tournament
The defending Europeans champions left it late, but a Jesus Navas goal in the 88th minute secured them a place in the knockout stages as group winners.
"It showed that a draw was good enough [for Spain]," Aragones told Marca. "They did not want to take risks, or they did not look for the victory quite so forcefully as they have on other occasions.
"The best thing you can say about Spain is that they played as they know how. They always remained true to their style and even though they did not have chances until the end of the match, I think they were the better side.
"For me, they are still the best team in the competition."
Navas' goal allowed Spain to keep top spot in Group C, as La Roja finished two points ahead of Italy, who defeated Republic of Ireland 2-0 on Monday.
"Qualification in first place is without discussion," the 73-year-old noted. "We were the best team in the group.
"Even though we did not play good first halves against Italy or Croatia, we have shown our potential. Only Germany have been superior so far."
Spain will now face England, France or Ukraine in the quarter-finals, but Aragones stated that La Roja's biggest threats lie elsewhere.
"Even Germany have not shown their best side," he added. "They have more [to give] and they will surely show it in the next rounds.
"From what I have seen, I have liked Portugal. They could be an alternative. They have three forwards who can cause problems to anyone and they have players who want the ball."