The honest reality: most restaurants within walking distance of the falls trade on the view, not the food. Three exceptions worth your money.
AG at Sterling Inn & Spa — chef-driven Niagara cuisine, walking distance from the falls, reasonable pre-fix lunch.
Weinkeller Restaurant — Bavarian-leaning menu, the schnitzel is genuinely good, and the wine list leans local.
Antica Pizzeria — Neapolitan wood-fired pizza, popular with locals, ten minutes from the tourist core.
If you want the view and don't mind paying for it, Skylon Tower's revolving dining room is the better of the two tower restaurants — Table Rock is fine but less special. Book the early sitting; the falls are floodlit but the river itself disappears once it is fully dark.