In a lot of ways, I think some of the simpler, non signature, table service restaurants are a good value. The buffets/family style dining places aren't a great value if you're not a heavy eater - and the quality can be poor. But if you're looking for good food and not a pig trough, you have some options.
In MK, I'd recommend the Plaza Restaurant for price/value and the food is pretty decent, but American blandness. A good example is the club sandwich, it's about $17 at the Plaza. A similar sandwich at a very popular local chain in my area is about $14. So not an extreme markup.
In Epcot, I consider Chefs de France an excellent value. The food is very good and exactly what I expect at a traditional French bistro in the 'burbs. In my hometown, DH and I have a favorite French place for dinner and then a movie (

oh god I miss going to the movies). Anyway, for a good comparison, the salmon entree at my local place is $28, at Chefs, it's $31. Again, it's that $3 markup. And what's crazy, onion soup is $11 at my local place, only $10 at Chefs.....
At AK, I prefer Yak & Yeti. I have a Landry's card, so the rewards are awesome and the food is just really good. Not too expensive. Always satisfying. At Y&Y, the teriyaki chicken entree is $25. At my local sit-down Japanese restaurant, it's $21. $4 markup.
At HS, go for Mama Melrose. The good is way better than Olive Garden and there's not too much sticker shock. Caprese salad at Mama's is $10, at my local fancy Italian restaurant it's $11. At my local place, the shrimp entrees are about $24, $25 at Mama's. So about the same as real world prices.
At the resorts, I consider the Wave a fantastic value. High quality ingredients and preparation, it's pretty close to what you'd get at a high-end steakhouse. At my favorite local place, the steak entree runs about $32 and a soup is $7. Similar entree is $34 and a soup is $9.50 at the Wave. Not too shabby.