Fist off, the "3D" portion of Frogger 3D refers to more than just the system it is on, or the fact that you can use the 3DS' 3D capabilities with the game. It also takes the game away from the classic top-down perspective and goes in pretty much every other direction it can. There are levels that will return you to the classic bird's-eye-view perspective, but you will also be faced with frog's-eye-view challenges that really adds a new spin on the game's standard presentation.
All of the cars, critters and frogs (Frogger has friends this time around) are fairly well detailed 3D models and only really show any kind of jaggedness when it seems appropriate for the game; in other words, when Frogger 3D hearks back to its more lower resolution roots.
Of course, the system's 3D functionality comes into play here as well. Not only does the game look good with the added depth, but there were times when it really helped the gameplay, especially when dealing with the levels where items were coming at the screen. That being said, Frogger 3D isn't beyond the occasional cheap 3D gag like having your amphibious hero come flying at the screen when he gets hit.
While the game's sound isn't anything that will win any awards, it gets the job done. The music is fun and has elements of the original theme song, while the various noises coming from the streets and rivers Frogger is trying to cross seem fitting to their environment. Again, it works and meets the requirement, but Frogger 3D doesn't need the sound turned on to make or break the overall experience.