It's hard to compare the signatures to chains outside the World because there are so few that make for a good comparison.
But just to provide my frame of reference as far as chain table service restaurants go . . .
To me, the low end (Level 1) are chains like Denny's, Friendly's, and Applebees. In my book, most fast food chains serve better food than these places. I'm also not a fan of Red Lobster.
Next up (Level 2) are chains like Chli's, Olive Garden, and Outback. To me, these are just okay.
Somewhat better (Level 3) are chains like P.F. Chang's, Macaroni Grill, and Texas Roadhouse. I generally enjoy these places and find the food to be good but not great.
Above these (Level 4) are places like Bonefish Grill, Hillstone Group Restuarants (Houston's etc.) and some of the Brazilian steakhouses (e.g., Fogo de Chao, Tejas de Brazil, etc.). I really enjoy these places and usually find the food to be quite good.
Yet above those (Level 5) are places like Morton's and Ruth's Chris. I rarely frequent those unless on an expense account (not enough bang for my buck relative to the next level down).
Now back to Disney . . .
To me, most of the dining plan signatures are at least as good, if not somewhat better, than Level 4. While I definately think some of these are better than others (and approach Level 5), to my palatte, there's not an enormous amont of difference between the best and worst of them.
In contrast, the non-signatures are all over the place. Some are closer to Level 1 while others approach Level 4. I will say that the best of these are a better deal than the average signature (either OOP or
DDP). For example, I'd put Via Napoli at nearly Level 4 (by way of comparision, I'd put California Pizza Kitchen somewhere between Level 2 and 3 and Pizza Hut and Domino's closer to Level 1).