Well my oppinion on the phases are as follows
Cell: Compared that this is a pretty fun phase it ends far too early and you never feel like your Cell gets particularly powerful with the low amount of DNA they give you. We can somewhat forgive them compared that this is supposed to be the tutorial phase... however there is just a lot they could have done... It feels like it ends right after it gets good especially since right before it gets good the cells start to get interesting (Mother Cells for example start to appear)
Creature: Being Social during this phase is totally stupid in everyway possible and they successfully make it not fun to do... Offensive is kinda... walk around and kill things... and a mix doesn't help. Probably the worst phase.
-Creature is my favorite editor however.
Tribal: There is so much you should have been able to do... while it is fun it is rather weak. This section isn't just shallow, it is lacking.
Civilisation: I actually like this phase quite a bit though there are so many problems with this phase... It is too late for a full review of this phase but lets sum it up as... Shallow and quickly becomes too easy even on Hard.
Space: This is my favorite phase and obviously the one they paid the most attention to. A lot of the worst parts of this phase disapear once you get far enough (such as really annoying Teraforming)
Creature, Tribal, Cell, Civilisation, Space In order of worst to Favorite!