It's difficult to translate into idiomatic Russian while staying true to the original, so the translator needs to get creative.
The most vapid rendering i can offhand come up with is
Великолепная возможность / Великолепный шанс
Attributive use of the word век - века is a customary device to express in Russian uniqueness, rarity, singularity, significance of an event, e.g. ограбление века, процесс века
One in my opinion good fully idiomatic rendering which after a while popped up in my head would be