I am going to list everywhere I remember going on vacation in order of which places I liked most. I have a thirst for international travel that I have yet to slake beyond Central America, so my future vacations are my real "favorites," but only in my mind.
Costa Rica (all over, focus on rainforest)
New York City (Manhattan)
Grand Canyon/Southwest tour (Flagstaff, Sedona, Phoenix, Albuquerque, Santa Fe, Carlsbad)
Los Cabos, Mexico
New Orleans, LA
Philadelphia, PA, San Antonio, Houston, and Dallas-Fort Worth, TX, areas
Michigan lake camping
Sarasota and St. Petersburg, FL, Disney/Orlando (tie)
Detroit area, Chicago, St. Louis, Roanoke (tie, given that I have barely spent any time in these places)
South Texas Coast, Jacksonville, FL, Wide swath of West Texas (tie)
The main things I do like are lots of free time, good food, museums, some amazing sights, and something 'cool' to do in the evenings. Friendly people or something I cannot find at home really help!
I don't care for places with nothing but chain restaurants; I don't love camping; I really dislike theme parks. The more time I spend somewhere, the more I like it -- with the exception of the last-place places in my list. I think it might just be a bad cultural fit in some cases.