I'm a big Colors fan, and upon playing a few rounds of it after seeing this thread, one thing I've been thinking about is just how damn cool the environments are. They're all great, but three in particular really stand out to me. Tropical Resort is an awesome introduction. The concept alone is incredible, a tropical resort hotel in outer space, and there are so many fantastic details. The line of flying cars gliding through the background, the hotel entryways along the "shopping street" paths, the water features and stacked buildings. Most of all, the tiki motif is a great way to do a classic Sonic throwback that's more original and exciting than just remaking an existing zone, and it's accented nicely by the surf music. Planet Wisp is very evocative of Sonic CD (the bassline in the music tracks makes me think of Quartz Quadrant past), and it's the best representation of the "nature and technology" clash in the franchise. It's a great narrative element to put you right in the middle of Eggman's destruction of a natural world, and again, wonderful details abound, like the metal pathways patching over the grass and especially the caution signs with the Eggman logo and strange language (similar to Collision Chaos). Aquarium Park is another brilliant concept. Someone suggested a while back that this zone is a nod to a Feudal Japan zone that was planned for Sonic 1, and while I can't say if that's true, it's stuck with me as such a cool idea. This zone has the most beautiful vistas in the whole game, particularly the opening downhill road in Act 1 where the massive cityscape unfolds before you, and the cascading river towards the end of Act 6. The Japanese architecture is blended nicely with the modern industrial elements like the tube passageways and smaller aquarium tanks, and the undersea areas themselves are lush and colorful. The three things that matter to me in a Sonic game, in order, are gameplay, music, and environment design. Colors satisfies all three, but the environment design is phenomenal, and the best of all the 3D games if you ask me. It's mind-boggling to me that some people say Colors is where Sonic Team "stopped trying", the imagination on display in these zones is the polar opposite of apathetic.