I've seen sunsets in Tuscany, Greece, on the coast. None compare to the Delta.
Why it's different
In the Danube Delta, the horizon is 360 degrees. No hills, no buildings. When the sun sets, color spreads in all directions simultaneously.
Best spot
The main pontoon, facing west. Bring a glass of wine.
When
Summer: sunset between 20:30 and 21:15. Most spectacular after a cloudy day.