Raul Garcia struck late as Atletico claimed a 1-1 draw at Real Madrid on Tuesday, leaving them well placed ahead of Friday's second leg.
James Rodriguez had given Real an 81st-minute lead, but Simeone was delighted with the character his team showed in response.
"They scored the goal against us at the end and we still found the strength to tie and have a 50-50 chance at home," Simeone said.
"They have very good players and that's a lot when you think you can win with a 0-0."
Simeone, whose side had chances throughout the first half, said the clash at The Santiago Bernabeu was played just as his team wanted.
"We set out for a match within the characteristics of the team that we are, so we could have our chances," the Argentine said.
"We played more as we wanted than as they wanted, we defended close to our box and we had three or four chances to score."
Simeone praised Mario Mandzukic and Saul, who both had first-half opportunities but were denied by Real goalkeeper Iker Casillas.
But it was the organisation of his reigning La Liga champions with which he was most pleased.
"Once more, the team showed that when they work together, they usually respond," Simeone said.
"We all work organised without allowing goal situations."