Bayern won the Bundesliga by a record margin of 25 points last season, and Voller cannot see a way his or any other club can bridge that gap.
"They have never had a squad like they have now," he said. "They don't just have 11 top players, or 15, they have 22 really top players.
"It really is overwhelming for the other clubs. Now they have also got a player like Thiago (Alcantara) for the midfield shows just how far away they are. They are miles in front."
With Borussia Dortmund also strengthening with the likes of Henrikh Mkhitaryan and Pierre-Emerick Aubameyang, Voller believes third place is the best his club can aim for this season.
"Coming third is more of a priority than winning the DFB-Pokal," he told the Bild am Sonntag newspaper.
"It would be a real season-long achievement."