I've got bests and worsts in different categories..=D
Best small airport terminals:
John Wayne/Orange County - simple, easy to get around, spotless.. the only problem is the permanent aroma de McDonald's..
Santa Barbara - beautiful terminal (there's a picture posted on the site here), not sure about now, but Carrow's was open upstairs and lunch on the balcony overlooking the entire airport was always fun..
Worst small airport terminals:
The old Ontario (ONT) terminal - I've seen airports in third-world countries that look more impressive. Never had I thought I would ever see portable classrooms double as waiting areas.
Burbank - the terminals at BUR just scream cramped and crowded, from the narrow hallways to the close proximity to the runways (if you could throw a rock from the Southwest gates, you might hit a flaring airliner).
Best large airport terminals:
Denver - I may be in the distinct minority here, but I really like DEN. Sure, everything is a long walk away, but that just means there's more to see!
Worst large airport terminals:
Kai Tak - I had heard so much about Kai Tak and was thrilled to visit.. the aviation action did not disappoint, but the terminal sure did. Just one big, extremely crowded hallway, a few newstands and the most expensive cafeteria I've ever eaten at.
Singapore Changi - While most people love this place, I found it too sterile. "Children's Play Quadrant Sector 17G-4".. an exageration, but that's the feeling I got there.
Delta's terminal at DFW (not sure what number it is) - "We'd like to welcome you to Dallas-Fort Worth.. we'll be arriving at Gate 3.. the current time is 11:43am.. we'll now announce connecting flights.. Nashville, 12:05, Gate 633. Boston, 12:00, Gate 514. Tampa, Gate 4, 12:30. New Orleans, 11:55, Gate 847." I'm sure they're not alone in this practice and it's not something really worthy of a complaint, but how many times has that happened to you? Why can't I be the guy going to Tampa for once? Instead I get to trudge down 7 miles of hallway, past 13 barbeque places, feeling obligated to stop in the "Everything Texan" to pick up some salt and pepper shakers in the shape of cowboy boots. I guess it's not so much a problem with DFW as it is with the hub and spoke system in practice.