I think it really depends on the couple, everyone is so different. Will there be a large party celebrating with them? Will they be going into the parks?
DH and I have had lots of anniversary dinners at WDW - Cali Grill (2), but our ADR time was much later than most and not as noisy and the food was not on par one of those nights, but wishes was wonderful. Narcossee,(2) has been pretty on point for us great food, service, water parade then the fireworks all really stellar. But we also have eaten at Ray's in MK and gotten ice cream from Main Street Ice Cream Parlor and watched parade, fireworks all magical and special for us as well.
We celebrated my parents anniversary one year at Spoodles when it was open, this was my parents choice, after we walked around the boardwalk watched the entertainers , and stood on the bridge to catch some of the fire works. Another year on their anniversary they wanted to spend the day at MK as a family so we did just that, QS meals and snacks all day, lots of rides, ending with parade and fireworks, really a wonderful day, lots of fun memories.