If I had to choose, seafood/fish. Having a shore lunch with fish caught 5 minutes previously is outstanding. I also have an excellent lobster bisque recipe. Breafeast out is also a favorite.
But all food is great, from a hole-in-the-wall falafel place to a 3-star Michelin restaurant. When I eat abroad, I rarely remember the the name of the place. Best sushi I had was in Encino. The best salmon was in Seattle (yes, a cliche). The best pizza was surprizingly in Munich.
For local Chicagoland places, I like:
Topolobambo/Frontera Grill/XoCo
Don Juans
Zias
Armands
Trotters (yes, I ate there once, the client paid)
Nookies
Johns
Janes
Sunda
The Weiner Circle
Taquera las Cumbres
Kikis
Twin Anchors