Universal's atmosphere theming is up to par to Disney's, but not the same as Disney. You can't expect it to be like Disney because the two are shooting for different things.
Universal Studios Florida is supposed to be a movie studio. A lot of people complain that there's no fantastical atmosphere when entering the park, but that's because that area is what you would see once inside the gates of a movie studio in Hollywood.
The Front Lot, which actually starts outside of the park, mimics the production offices and administrative buildings of a movie studio, with it's guest services offices and stores. Production Central is seemingly un-themed, except for the fact that it's exactly what the sound stage area of a Hollywood movie studio looks like.
The rest of the park is what would be considered the Back Lot area of a studio. A "back lot" is where the fake outdoor sets are located. For example, the New York area is actually a montage of different parts of New York in different eras. All of it is as highly detailed as you would expect a movie set would be. Some people complain that its not totally impressive because you can tell that its all sets. What they don't understand is that this area isn't supposed to be New York... it's supposed to be a movie set version of New York. It's purpose is not to make you believe your actually in New York, but that your on a movie studio back lot set of New York.
The rest of the park is similar. The San Francisco area is a back lot version of San Francisco bay, and the Hollywood area is a conglomerate of Hollywood Blvd and Beverly Hills . The Expo Center, where Back To The Future and MIB are located, is supposed to double as a World's Fair type setting. The Amity area is similar, but I believe it's actually supposed to make you feel your in the fictional town from Jaws. The KidZone's atmosphere is not totally cohesive but the individual areas, like Fivels Playland and Curios George Goes To Town, are highly themed.
Here's a hint. The walk from the Hollywood area to and the Expo Center may seem kind of dull, until you realize youre right between the East Coast and the West Coast. On your left is Central Park and on your right is a Beverly Hills-esque Spanish Villa apartment complex. For a more appealing and less congested walk, take a stroll through Central Park, or make a right into the apartment set and take a shortcut to the KidZone.
Universal Studios was designed so that any part of it could be used on a movie shoot. While Disney parks are considered a stage, with everything going on inside of them a show, Universal Studios is more like a behind the scenes peek. At Disney you can stand back and see the big picture, but at Universal you have to look at the details and ideas behind everything to fully enjoy it.
I discussed the Studios park mainly because that's what most Disney fans point to as being a lack of theme and atmosphere at Universal. I could go over the rest of the resort if you'd like.
-Kevin