Tabernash Tavern is by far the best restaurant in the area, but it's in Tabernash, not Winter Park. There are a couple of restaurants at Devil's Thumb Ranch that are supposed to be good, but you have to be staying at the resort to eat there.
I'm personally not a fan of Deno's, but a lot of locals like it.
My top 5 in the area would probably be:
1. Tabernash Tavern (Tabernash) - by far and away the best restaurant in Grand County. We eat here regularly.
2. Fitch Ranch Cafe (Granby) - they own a ranch and sell their own meat at the restaurant. Very good. Also has a store attached where they sell the meat from their ranch.
3. Grand Azteca (Granby) - the one in Fraser now has different ownership and has gone downhill. They used to be owned by the same family.
4. Volario's (Winter Park) - good, but not great Italian.
5. Fontenot's (Winter Park) - good, but not great Cajun place. If you're in Houston or thereabouts, I'd pass on this one.
Hernando's is good, just insanely crowded. We don't go there much.