first of all you cant go wrong with any one of them.
Second, if you wanna give yourself some contrast go with either Orchid or Morningrise. They are much darker, much blacker, as someone mentioned. They are also the most unique. I prefer Morningrise as it is my all time favorite CD out of the whole fuckin world.
If you dont wanna challenge yourself AS much, go with still life. Its kinda easier to get into, and overall has a nice, clean, almost classical rock (some moments) feel to it. MAYH is kinda the middle ground between all of those, and its definitely either my 2nd or 3rd fav. It has my favorite story when it comes to lyrical concept. Its also nice and sad.
I guess it depends on the feeling you like to find in your music. Still life is in my opinion the happiest of all these albums. Not that its happy or anything....
Morningrise and Orchid have the greatest "I'm lost in the forest and its midnight" type of feel, and I prefer Morningrise as it flows more cohesively.
ok thats it.