Vicente del Bosque's charges are looking to bounce back from their group-stage exit at the 2014 World Cup by winning their third-straight European Championships in France this summer.
Results in preparation for the Euros have been less than impressive, though, with Spain drawing 1-1 with both Italy and Romania in their latest round of friendlies in March.
But despite not having huge amounts of momentum behind them, Aduriz believes Spain are the top contenders for the tournament because they have been there and done it in recent years.
"Today, the best team is the one with the most options. Spain is favourite because they are the reigning champion and because they have shown that they are able to compete with the best," he told Sportium News.
"Spain has been the dominant force in recent years. They have earned that credit."
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The 35-year-old Athletic Club striker has scored 31 goals in all competitions this season, which he has described as the best of his long career, surpassing the 26 he netted last term.
Despite his age, his goalscoring exploits earned him selection in Vincent Del Bosque's squad last month, scoring his first goal in the draw against Italy.
Aduriz admits he dreams of turning out for his country at the Euros but is well aware that he still has a lot to do in order to convince Del Bosque to pick him for the finals.
"I try to do my best work. I'd love to go [to Euro 2016], but the decision is not in my hands, he added.
"I'm under no illusions. There is still a long time until June.
"Before then, I have some nice challenges with Athletic."