At DFW, terminal E is pretty pathetic as far as food goes (dickey's bbq is meh, the mexican place is always over-crowded, the TGIF down the way never seems to be open, and the food courts are lame - they do have Haagen Dazs, though, if you're a UA flyer and willing to walk). The AA terminals are much better, admittedly.
LGA is nothing to write home about, although I'm a sucker for Mexijoe's carnitas tacos on corn tortillas with a cold bottle of Jarritos, and 5 guys is always decent if extremely slow. But what do they have otherwise? Jet's bar and Grill? NY Sports bar and grill? The generic Chinese place? Meh...
ORD does have some pretty solid options, though. I'm a fan of Berghoff, like Billy Goat for a quick cheeborger or brat, and love the Goose Island Marisol at Tortas Frontera. and I admit, I also like the hot dogs at America's Dog. I know, not particularly high-brow.