On Accelerated Evolution, Devy decided to strip it down a little bit. There are fewer layers and some of the songs are more straightforward. I actually really like that aspect of it. Sure, it's cool to discover new subleties in Terria with every listen but it's also nice to just rock out sometimes.
As for his other material, it's tough to say. The general consensus is Ocean Machine and Terria are "the best." Those show his more proggy tendencies well and have some pretty intricate bits going on. Infinity has a lot of layers and quite obviously comes from the period when Devy went completely mad. So it's a bit less accessible than the previous two I mentioned but very much worth absorbing. As for Physicist... it's a much maligned beast. It sounds like "strapping light" to many and the prodution's kinda meh. However, a lot of the songs-while not exactly moving his sound forward- are extremely catchy. It's the one Devy release I can think of where a cluster of songs sounds alike ("material," "viloence," the opener whose name escapes me, "death"). So if you expect something like Terria, Physicist will let you down. However, it's still a really cool disc.