Serious answer: current winner for nicest hotel in Houston is the Post Oak in uptown. If money is no object, stay there and uber downtown as needed.
Actual downtown: JW Marriott or Four Seasons are the best properties depending on which one has been renovated more recently and which points system you prefer.
Mid range, you can usually get the Hilton Americas, Hyatt Regency, or Le Meridian pretty cheap if no conventions are in town. Qatar Airways flight crews stay at Le Meridian and the girls are easy on the eyes. The rooftop bar there is seriously cool. Hyatt Regency has the highest hooker capacity of all hotels in Houston.
Cheap: the Holiday Inn by Toyota Center, Marriott Courtyard by HPD headquarters, or Hampton Inn near ballpark.
Free: tent village under 59 bounded by Chartres, Ruiz, and Hamilton St. or homeless colony along Caroline Street under I-45. At the first place, you will get shanked. Tony Buzbee recently stayed at the second place. During the freeze, I drove by and spotted the more industrious denizens of that community warming themselves over a shipping palate they set on fire.